Series: WAMU 2007-OA3	Washington Mutual
Issue Date: 03/27/2007
Record Date: 05/31/2007
Distribution Date: 06/25/2007

Summary Collateral Information
	Description
Group 1
Pool 8086	Option ARM
Pool 8087	Option ARM
Pool 8088	Option ARM

General Information
Description	Total	Pool 8086	Pool 8087	Pool 8088	Group 1
Weighted Average Pass Through Rate	6.51109%	6.49732%	7.44104%	6.45557%	6.51109%
Weighted Average Mortgage Interest Rate	7.80020%	7.89081%	7.81604%	7.77667%	7.80020%
Weighted Average Remaining Term (in Months)	407.68304	399.11149	380.00697	411.22840	407.68304
Weighted Average Loan Age (in Months)	3.33236	3.26474	4.51765	3.28913	3.33236
Average Ending Scheduled Principal Balance	$547,356.83	$261,078.74	$737,142.89	$740,557.12	$547,356.83
Remaining Loan Count	1830	737	53	1040	1830
Ending Scheduled Principal Balance	$1,001,663,002.23	$192,415,028.56	$39,068,573.29	$770,179,400.38	$1,001,663,002.23

Series: WAMU 2007-OA3	Washington Mutual
Issue Date: 03/27/2007
Record Date: 05/31/2007
Distribution Date: 06/25/2007

Geographic Distribution
Total			Pool 8086			Pool 8087
State	Percent	Ending Scheduled Principal Balance	State	Percent	Ending Scheduled Principal Balance	State	Percent	Ending Scheduled Principal Balance
CA	$637,348,844.90	63.63%	CA	$95,711,725.38	49.74%	CA	$34,228,512.88	87.61%
FL	$84,638,762.64	8.45%	FL	$18,870,440.10	9.81%	IL	$2,081,237.44	5.33%
NY	$42,064,637.37	4.20%	WA	$11,457,483.27	5.95%	WA	$1,963,462.35	5.03%
WA	$33,440,069.80	3.34%	AZ	$6,577,290.47	3.42%	NY	$288,008.26	0.74%
AZ	$20,501,926.01	2.05%	IL	$6,328,425.22	3.29%	WI	$287,510.75	0.74%
OTHER	$183,668,761.51	18.34%	OTHER	$53,469,664.12	27.79%	OTHER	$219,841.61	0.56%

Series: WAMU 2007-OA3	Washington Mutual
Issue Date: 03/27/2007
Record Date: 05/31/2007
Distribution Date: 06/25/2007

Geographic Distribution
Pool 8088			Group 1
State	Percent	Ending Scheduled Principal Balance	State	Percent	Ending Scheduled Principal Balance
CA	$507,408,606.64	65.88%	CA	$637,348,844.90	63.63%
FL	$65,768,322.54	8.54%	FL	$84,638,762.64	8.45%
NY	$36,949,047.51	4.80%	NY	$42,064,637.37	4.20%
WA	$20,019,124.18	2.60%	WA	$33,440,069.80	3.34%
CO	$15,017,946.11	1.95%	AZ	$20,501,926.01	2.05%
OTHER	$125,016,353.40	16.23%	OTHER	$183,668,761.51	18.34%

Series: WAMU 2007-OA3	Washington Mutual
Issue Date: 03/27/2007
Record Date: 05/31/2007
Distribution Date: 06/25/2007

Prepayment Information (all groups)
	1 Month	3 Month	6 Month	12 Month	Cumulative
PSA	2937.74528%	5184.61132%	5184.61132%	5184.61132%	5184.61808%
CPR	19.57925%	24.35195%	24.35195%	24.35195%	24.35194%
SMM	1.79943%	2.29882%	2.29882%	2.29882%	2.29882%

Trigger Events
	Trigger Flag
Optional Termination Date Has Occurred; 1=Yes, 0=No	0
Senior Prepayment Step-Down Has Occurred; 1=Yes, 0=No	0
Senior Credit Support Depletion Date Has Occurred; 1=Yes, 0=No	0

Comments

1. The Class B Certificates provide, to the limited extent described in the Prospectus Supplement, credit support, to certain Senior Certificates. The "Prospectus Supplement" is that certain Prospectus Supplement, dated March 23, 2007 to that certain Prospectus Supplement, dated March 22, 2007, to which certain Senior Certificates were offered.

2. The MBA method of delinquency calculation is used.

Series: WAMU 2007-OA3	Washington Mutual
Issue Date: 03/27/2007
Record Date: 05/31/2007
Distribution Date: 06/25/2007

Certificate Payment Summary Report
Class	CUSIP	Original Principal/Notional Balance	Beginning Principal/Notional Balance	Interest Distribution	Principal Distribution	Principal Loss	Deferred Interest	Total Distribution	Ending Principal/Notional Balance
1A	93364AAA0	$140,139,000.00	$138,533,075.44	$668,036.53	$149,765.38	$0.00	$0.00	$817,801.91	$138,383,310.06
2A	93364AAB8	$408,000,000.00	$382,451,322.99	$1,847,450.29	$7,654,515.75	$0.00	$0.00	$9,501,966.04	$374,796,807.24
2A1A	93364AAC6	$165,000,000.00	$154,667,814.44	$745,841.73	$3,095,576.22	$0.00	$0.00	$3,841,417.95	$151,572,238.22
2A1B	93364AAD4	$55,817,000.00	$52,321,778.18	$252,306.96	$1,047,186.53	$0.00	$0.00	$1,299,493.49	$51,274,591.65
CA1B	93364AAE2	$96,121,000.00	$90,998,186.93	$434,111.92	$1,493,397.57	$0.00	$0.00	$1,927,509.49	$89,504,789.36
CA1B_GRP1	XXXXXXXXX	$17,518,000.00	$17,317,252.27	$82,612.91	$18,721.34	$0.00	$0.00	$101,334.25	$17,298,530.93
CA1B_GRP2	XXXXXXXXX	$78,603,000.00	$73,680,934.66	$351,498.99	$1,474,676.23	$0.00	$0.00	$1,826,175.22	$72,206,258.43
CA1C	93364AAF9	$96,121,000.00	$90,998,186.93	$440,380.68	$1,493,397.57	$0.00	$0.00	$1,933,778.25	$89,504,789.36
CA1C_GRP1	XXXXXXXXX	$17,518,000.00	$17,317,252.27	$83,805.88	$18,721.34	$0.00	$0.00	$102,527.22	$17,298,530.93
CA1C_GRP2	XXXXXXXXX	$78,603,000.00	$73,680,934.66	$356,574.79	$1,474,676.23	$0.00	$0.00	$1,831,251.02	$72,206,258.43
CXPPP	93364AAH5	$0.00	$0.00	$568,097.98	$0.00	$0.00	$0.00	$568,097.98	$0.00
CXPPP_IO_GRP1	XXXXXXXXX	$194,639,464.00	$192,602,236.62	$104,231.64	$0.00	$0.00	$0.00	$104,231.64	$192,415,028.56

Series: WAMU 2007-OA3	Washington Mutual
Issue Date: 03/27/2007
Record Date: 05/31/2007
Distribution Date: 06/25/2007

Certificate Payment Summary Report (Continued)
Class	CUSIP	Original Principal/Notional Balance	Beginning Principal/Notional Balance	Interest Distribution	Principal Distribution	Principal Loss	Deferred Interest	Total Distribution	Ending Principal/Notional Balance
CXPPP_IO_GRP2	XXXXXXXXX	$873,359,094.00	$823,995,269.29	$463,866.31	$0.00	$0.00	$0.00	$463,866.31	$809,247,973.67
CXPPP_PO_GRP1	XXXXXXXXX	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00
CXPPP_PO_GRP2	XXXXXXXXX	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00
2X1	93364AAG7	$94,334,073.00	$49,109,036.48	$56,291.92	$0.00	$0.00	$0.00	$56,291.92	$39,068,573.29
B1	93364AAJ1	$18,690,000.00	$18,659,669.52	$92,712.64	$116.31	$0.00	$0.00	$92,828.95	$18,659,553.21
B2	93364AAK8	$18,690,000.00	$18,659,669.52	$93,516.04	$116.31	$0.00	$0.00	$93,632.35	$18,659,553.21
B3	93364AAL6	$8,010,000.00	$7,997,001.22	$41,455.57	$49.85	$0.00	$0.00	$41,505.42	$7,996,951.37
B4	93364AAM4	$26,700,000.00	$26,656,670.74	$147,366.96	$166.16	$0.00	$0.00	$147,533.12	$26,656,504.58
B5	93364AAN2	$11,214,000.00	$11,195,801.72	$62,858.21	$69.79	$0.00	$0.00	$62,928.00	$11,195,731.93
B6	93364AAP7	$4,806,000.00	$4,798,200.73	$26,939.23	$29.91	$0.00	$0.00	$26,969.14	$4,798,170.82
B7	93364AAQ5	$4,272,000.00	$4,265,067.32	$23,945.98	$26.59	$0.00	$0.00	$23,972.57	$4,265,040.73
B8	93364AAS1	$3,204,000.00	$3,198,800.49	$17,959.49	$19.94	$0.00	$0.00	$17,979.43	$3,198,780.55
B9	93364AAT9	$3,204,000.00	$3,198,800.49	$17,959.49	$19.94	$0.00	$0.00	$17,979.43	$3,198,780.55

Series: WAMU 2007-OA3	Washington Mutual
Issue Date: 03/27/2007
Record Date: 05/31/2007
Distribution Date: 06/25/2007

Certificate Payment Summary Report (Continued)
Class	CUSIP	Original Principal/Notional Balance	Beginning Principal/Notional Balance	Interest Distribution	Principal Distribution	Principal Loss	Deferred Interest	Total Distribution	Ending Principal/Notional Balance
B10	93364AAU6	$8,010,458.00	$7,997,459.25	$44,901.67	$49.86	$0.00	$0.00	$44,951.53	$7,997,409.40
R	93364AAR3	$100.00	$0.00	$0.03	$0.00	$0.00	$0.00	$0.03	$0.00
R_SYN	XXXXXXXXX	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00
TFEE	XXXXXXXXX	$0.00	$0.00	$677.73	$0.00	$0.00	$0.00	$677.73	$0.00
Total*		$1,067,998,558.00	$1,016,597,505.91	$5,582,133.33	$14,934,503.68	$0.00	$0.00	$20,516,637.00	$1,001,663,002.24

*Total balances exclude notional balances.

Series: WAMU 2007-OA3	Washington Mutual
Issue Date: 03/27/2007
Record Date: 05/31/2007
Distribution Date: 06/25/2007

Total Funds Available for Distribution
PRINCIPAL BALANCE
Scheduled Principal Received or Advanced	($3,419,993.95)
Unscheduled Principal	$911,020.26
Prepayments in Full	$17,443,477.37
Repurchases	$0.00
Liquidations	$0.00
Total Principal	$14,934,503.68
INTEREST
Accrued Interest at Gross Rate	$6,607,831.25
Relief Act Shortfall	$0.00
Prepayment Interest Shortfall	$0.00
Servicing Fees	$1,091,869.68
Other	$0.00
Total Interest	$5,515,961.72
ADDITIONAL FUNDS
Excess Liquidation Proceeds	$0.00
Subsequent Recoveries	$0.00
Prepayment Penalties	$66,171.60

Series: WAMU 2007-OA3	Washington Mutual
Issue Date: 03/27/2007
Record Date: 05/31/2007
Distribution Date: 06/25/2007

Total Funds Available for Distribution
ADDITIONAL FUNDS
Other	$0.00
Total Additional Funds	$66,171.60
Total Funds Available for Distribution	$20,450,465.40

Certificate Payment Report - Principal
Class	CUSIP	Beginning Principal/Notional Balance	Principal Distribution	Principal Loss	Principal Reimbursed	Subsequent Recoveries	Deferred Interest	Total Principal Distribution	Ending Principal/Notional Balance
1A	93364AAA0	$138,533,075.44	$149,765.38	$0.00	$0.00	$0.00	$0.00	$149,765.38	$138,383,310.06
2A	93364AAB8	$382,451,322.99	$7,654,515.75	$0.00	$0.00	$0.00	$0.00	$7,654,515.75	$374,796,807.24
2A1A	93364AAC6	$154,667,814.44	$3,095,576.22	$0.00	$0.00	$0.00	$0.00	$3,095,576.22	$151,572,238.22
2A1B	93364AAD4	$52,321,778.18	$1,047,186.53	$0.00	$0.00	$0.00	$0.00	$1,047,186.53	$51,274,591.65
CA1B	93364AAE2	$90,998,186.93	$1,493,397.57	$0.00	$0.00	$0.00	$0.00	$1,493,397.57	$89,504,789.36
CA1B_GRP1	XXXXXXXXX	$17,317,252.27	$18,721.34	$0.00	$0.00	$0.00	$0.00	$18,721.34	$17,298,530.93
CA1B_GRP2	XXXXXXXXX	$73,680,934.66	$1,474,676.23	$0.00	$0.00	$0.00	$0.00	$1,474,676.23	$72,206,258.43
CA1C	93364AAF9	$90,998,186.93	$1,493,397.57	$0.00	$0.00	$0.00	$0.00	$1,493,397.57	$89,504,789.36
CA1C_GRP1	XXXXXXXXX	$17,317,252.27	$18,721.34	$0.00	$0.00	$0.00	$0.00	$18,721.34	$17,298,530.93

Series: WAMU 2007-OA3	Washington Mutual
Issue Date: 03/27/2007
Record Date: 05/31/2007
Distribution Date: 06/25/2007

Certificate Payment Report - Principal (Continued)
Class	CUSIP	Beginning Principal/Notional Balance	Principal Distribution	Principal Loss	Principal Reimbursed	Subsequent Recoveries	Deferred Interest	Total Principal Distribution	Ending Principal/Notional Balance
CA1C_GRP2	XXXXXXXXX	$73,680,934.66	$1,474,676.23	$0.00	$0.00	$0.00	$0.00	$1,474,676.23	$72,206,258.43
CXPPP	93364AAH5	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00
CXPPP_IO_GRP1	XXXXXXXXX	$192,602,236.62	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$192,415,028.56
CXPPP_IO_GRP2	XXXXXXXXX	$823,995,269.29	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$809,247,973.67
CXPPP_PO_GRP1	XXXXXXXXX	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00
CXPPP_PO_GRP2	XXXXXXXXX	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00
2X1	93364AAG7	$49,109,036.48	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$39,068,573.29
B1	93364AAJ1	$18,659,669.52	$116.31	$0.00	$0.00	$0.00	$0.00	$116.31	$18,659,553.21
B2	93364AAK8	$18,659,669.52	$116.31	$0.00	$0.00	$0.00	$0.00	$116.31	$18,659,553.21
B3	93364AAL6	$7,997,001.22	$49.85	$0.00	$0.00	$0.00	$0.00	$49.85	$7,996,951.37
B4	93364AAM4	$26,656,670.74	$166.16	$0.00	$0.00	$0.00	$0.00	$166.16	$26,656,504.58
B5	93364AAN2	$11,195,801.72	$69.79	$0.00	$0.00	$0.00	$0.00	$69.79	$11,195,731.93
B6	93364AAP7	$4,798,200.73	$29.91	$0.00	$0.00	$0.00	$0.00	$29.91	$4,798,170.82

Series: WAMU 2007-OA3	Washington Mutual
Issue Date: 03/27/2007
Record Date: 05/31/2007
Distribution Date: 06/25/2007

Certificate Payment Report - Principal (Continued)
Class	CUSIP	Beginning Principal/Notional Balance	Principal Distribution	Principal Loss	Principal Reimbursed	Subsequent Recoveries	Deferred Interest	Total Principal Distribution	Ending Principal/Notional Balance
B7	93364AAQ5	$4,265,067.32	$26.59	$0.00	$0.00	$0.00	$0.00	$26.59	$4,265,040.73
B8	93364AAS1	$3,198,800.49	$19.94	$0.00	$0.00	$0.00	$0.00	$19.94	$3,198,780.55
B9	93364AAT9	$3,198,800.49	$19.94	$0.00	$0.00	$0.00	$0.00	$19.94	$3,198,780.55
B10	93364AAU6	$7,997,459.25	$49.85	$0.00	$0.01	$0.00	$0.00	$49.86	$7,997,409.40
R	93364AAR3	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00
R_SYN	XXXXXXXXX	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00
TFEE	XXXXXXXXX	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00
Total *		$1,016,597,505.91	$14,934,503.67	$0.00	$0.01	$0.00	$0.00	$14,934,503.68	$1,001,663,002.24

*Total balances exclude notional balances.

Series: WAMU 2007-OA3	Washington Mutual
Issue Date: 03/27/2007
Record Date: 05/31/2007
Distribution Date: 06/25/2007

Certificate Payment Report - Interest
Class	Beginning Principal/Notional Balance	Interest Rate Accrued	Interest Rate Paid	Interest Accrued	Prepayment Interest Shortfall	Relief Act Shortfall	Other Interest Shortfall	Unscheduled Interest	Interest Reimbursed	Carryforward Amount Paid	Total Interest Distributed	Total Carryforward Amount Remaining
1A	$138,533,075.44	5.7866600000%	5.7866600000%	$668,036.51	$0.00	$0.00	$0.00	$0.02	$0.00	$0.00	$668,036.53	$0.00
2A	$382,451,322.99	5.7966600000%	5.7966600000%	$1,847,450.24	$0.00	$0.00	$0.00	$0.05	$0.00	$0.00	$1,847,450.29	$0.00
2A1A	$154,667,814.44	5.7866600000%	5.7866600000%	$745,841.71	$0.00	$0.00	$0.00	$0.02	$0.00	$0.00	$745,841.73	$0.00
2A1B	$52,321,778.18	5.7866600000%	5.7866600000%	$252,306.95	$0.00	$0.00	$0.00	$0.01	$0.00	$0.00	$252,306.96	$0.00
CA1B	$90,998,186.93	5.5400000000%	5.5400000000%	$434,111.91	$0.00	$0.00	$0.00	$0.01	$0.00	$0.00	$434,111.92	$0.00
CA1B_GRP1	$17,317,252.27	5.5400000000%	5.5400000000%	$82,612.91	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$82,612.91	$0.00
CA1B_GRP2	$73,680,934.66	5.5400000000%	5.5400000000%	$351,498.99	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$351,498.99	$0.00
CA1C	$90,998,186.93	5.6200000000%	5.6200000000%	$440,380.67	$0.00	$0.00	$0.00	$0.01	$0.00	$0.00	$440,380.68	$0.00
CA1C_GRP1	$17,317,252.27	5.6200000000%	5.6200000000%	$83,805.88	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$83,805.88	$0.00
CA1C_GRP2	$73,680,934.66	5.6200000000%	5.6200000000%	$356,574.79	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$356,574.79	$0.00
CXPPP	$0.00	0.0000000000%	0.0000000000%	$514,609.63	$0.00	$0.00	$0.00	$0.02	$0.00	$0.00	$568,097.98	$0.00
CXPPP_IO_GRP1	$192,602,236.62	0.6658208842%	0.6494107763%	$106,865.49	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$104,231.64	$0.00

Series: WAMU 2007-OA3	Washington Mutual
Issue Date: 03/27/2007
Record Date: 05/31/2007
Distribution Date: 06/25/2007

Certificate Payment Report - Interest (Continued)
Class	Beginning Principal/Notional Balance	Interest Rate Accrued	Interest Rate Paid	Interest Accrued	Prepayment Interest Shortfall	Relief Act Shortfall	Other Interest Shortfall	Unscheduled Interest	Interest Reimbursed	Carryforward Amount Paid	Total Interest Distributed	Total Carryforward Amount Remaining
CXPPP_IO_GRP2	$823,995,269.29	0.5938055458%	0.6755373395%	$407,744.13	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$463,866.31	$0.00
CXPPP_PO_GRP1	$0.00	0.0000000000%	0.0000000000%	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00
CXPPP_PO_GRP2	$0.00	0.0000000000%	0.0000000000%	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00
2X1	$49,109,036.48	1.3755167278%	1.3755167278%	$56,291.92	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$56,291.92	$0.00
B1	$18,659,669.52	5.7700000000%	5.7700000000%	$92,712.64	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$92,712.64	$0.00
B2	$18,659,669.52	5.8200000000%	5.8200000000%	$93,516.04	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$93,516.04	$0.00
B3	$7,997,001.22	6.0200000000%	6.0200000000%	$41,455.57	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$41,455.57	$0.00
B4	$26,656,670.74	6.2362948152%	6.4199999387%	$143,150.13	$0.00	$0.00	$0.00	$0.00	$0.00	$4,216.83	$147,366.96	$0.00
B5	$11,195,801.72	6.2362948152%	6.5200003352%	$60,123.05	$0.00	$0.00	$0.00	$0.00	$0.00	$2,735.15	$62,858.21	$0.00
B6	$4,798,200.73	6.2362948152%	6.5199996534%	$25,767.02	$0.00	$0.00	$0.00	$0.00	$0.00	$1,172.21	$26,939.23	$0.00
B7	$4,265,067.32	6.2362948152%	6.5199990416%	$22,904.02	$0.00	$0.00	$0.00	$0.00	$0.00	$1,041.96	$23,945.98	$0.00
B8	$3,198,800.49	6.2362948152%	6.5200008568%	$17,178.02	$0.00	$0.00	$0.00	$0.00	$0.00	$781.47	$17,959.49	$0.00
B9	$3,198,800.49	6.2362948152%	6.5200008568%	$17,178.02	$0.00	$0.00	$0.00	$0.00	$0.00	$781.47	$17,959.49	$0.00

Series: WAMU 2007-OA3	Washington Mutual
Issue Date: 03/27/2007
Record Date: 05/31/2007
Distribution Date: 06/25/2007

Certificate Payment Report - Interest (Continued)
Class	Beginning Principal/Notional Balance	Interest Rate Accrued	Interest Rate Paid	Interest Accrued	Prepayment Interest Shortfall	Relief Act Shortfall	Other Interest Shortfall	Unscheduled Interest	Interest Reimbursed	Carryforward Amount Paid	Total Interest Distributed	Total Carryforward Amount Remaining
B10	$7,997,459.25	6.2362948152%	6.5200550836%	$42,947.50	$0.00	$0.00	$0.00	$0.00	$0.00	$1,954.17	$44,901.67	$0.00
R	$0.00	0.0000000000%	0.0000000000%	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.03	$0.00
R_SYN	$0.00	0.0000000000%	0.0000000000%	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00
TFEE	$0.00	0.0000000000%	0.0000000000%	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$677.73	$0.00
Total *	$1,016,597,505.91			$5,515,961.55	$0.00	$0.00	$0.00	$0.15	$0.00	$12,683.26	$5,582,133.33	$0.00

*Total balances exclude notional balances.

Series: WAMU 2007-OA3	Washington Mutual
Issue Date: 03/27/2007
Record Date: 05/31/2007
Distribution Date: 06/25/2007

Principal Factors Report
Class	Original Scheduled Balance	Beginning Principal/Notional Balance	Principal Loss	Principal Reimbursed	Subsequent Recoveries	Deferred Interest	Total Principal	Ending Principal/Notional Balance Percent	Ending Principal/Notional Balance
1A	$140,139,000.00	988.54048794	0.00000000	0.00000000	0.00000000	0.00000000	1.06869166	0.9874717963	987.47179629
2A	$408,000,000.00	937.38069360	0.00000000	0.00000000	0.00000000	0.00000000	18.76106801	0.9186196256	918.61962559
2A1A	$165,000,000.00	937.38069358	0.00000000	0.00000000	0.00000000	0.00000000	18.76106800	0.9186196256	918.61962558
2A1B	$55,817,000.00	937.38069370	0.00000000	0.00000000	0.00000000	0.00000000	18.76106795	0.9186196257	918.61962574
CA1B	$96,121,000.00	946.70453834	0.00000000	0.00000000	0.00000000	0.00000000	15.53664204	0.9311678963	931.16789630
CA1B_GRP1	$17,518,000.00	988.54048807	0.00000000	0.00000000	0.00000000	0.00000000	1.06869163	0.9874717964	987.47179644
CA1B_GRP2	$78,603,000.00	937.38069361	0.00000000	0.00000000	0.00000000	0.00000000	18.76106803	0.9186196256	918.61962559
CA1C	$96,121,000.00	946.70453834	0.00000000	0.00000000	0.00000000	0.00000000	15.53664204	0.9311678963	931.16789630
CA1C_GRP1	$17,518,000.00	988.54048807	0.00000000	0.00000000	0.00000000	0.00000000	1.06869163	0.9874717964	987.47179644
CA1C_GRP2	$78,603,000.00	937.38069361	0.00000000	0.00000000	0.00000000	0.00000000	18.76106803	0.9186196256	918.61962559
CXPPP	$0.00	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.0000000000	0.00000000

Series: WAMU 2007-OA3	Washington Mutual
Issue Date: 03/27/2007
Record Date: 05/31/2007
Distribution Date: 06/25/2007

Principal Factors Report (Continued)
Class	Original Scheduled Balance	Beginning Principal/Notional Balance	Principal Loss	Principal Reimbursed	Subsequent Recoveries	Deferred Interest	Total Principal	Ending Principal/Notional Balance Percent	Ending Principal/Notional Balance
CXPPP_IO_GRP1	$194,639,464.00	989.53332825	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.9885715086	988.57150860
CXPPP_IO_GRP2	$873,359,094.00	943.47820381	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.9265924855	926.59248553
CXPPP_PO_GRP1	$0.00	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.0000000000	0.00000000
CXPPP_PO_GRP2	$0.00	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.0000000000	0.00000000
2X1	$94,334,073.00	520.58641081	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.4141512398	414.15123982
B1	$18,690,000.00	998.37718138	0.00000000	0.00000000	0.00000000	0.00000000	0.00622311	0.9983709583	998.37095827
B2	$18,690,000.00	998.37718138	0.00000000	0.00000000	0.00000000	0.00000000	0.00622311	0.9983709583	998.37095827
B3	$8,010,000.00	998.37718102	0.00000000	0.00000000	0.00000000	0.00000000	0.00622347	0.9983709576	998.37095755
B4	$26,700,000.00	998.37718127	0.00000000	0.00000000	0.00000000	0.00000000	0.00622322	0.9983709581	998.37095805
B5	$11,214,000.00	998.37718209	0.00000000	0.00000000	0.00000000	0.00000000	0.00622347	0.9983709586	998.37095862
B6	$4,806,000.00	998.37718061	0.00000000	0.00000000	0.00000000	0.00000000	0.00622347	0.9983709571	998.37095714
B7	$4,272,000.00	998.37718165	0.00000000	0.00000000	0.00000000	0.00000000	0.00622425	0.9983709574	998.37095740
B8	$3,204,000.00	998.37718165	0.00000000	0.00000000	0.00000000	0.00000000	0.00622347	0.9983709582	998.37095818

Series: WAMU 2007-OA3	Washington Mutual
Issue Date: 03/27/2007
Record Date: 05/31/2007
Distribution Date: 06/25/2007

Principal Factors Report (Continued)
Class	Original Scheduled Balance	Beginning Principal/Notional Balance	Principal Loss	Principal Reimbursed	Subsequent Recoveries	Deferred Interest	Total Principal	Ending Principal/Notional Balance Percent	Ending Principal/Notional Balance
B9	$3,204,000.00	998.37718165	0.00000000	0.00000000	0.00000000	0.00000000	0.00622347	0.9983709582	998.37095818
B10	$8,010,458.00	998.37727755	0.00000000	0.00000125	0.00000000	0.00000000	0.00622436	0.9983710544	998.37105444
R	$100.00	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.0000000000	0.00000000
R_SYN	$0.00	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.0000000000	0.00000000
TFEE	$0.00	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.0000000000	0.00000000

Interest Factors Report
Class	Original Balance	Interest Rate Accrued	Interest Rate Paid	Current Month Interest Accrued	Prepayment Interest Shortfall	Relief Act Interest Shortfall	Other Interest Shortfall	Unscheduled Interest	Interest Reimbursed	Carryforward Amount Paid	Deferred Interest	Total Interest Distribution	Total Carryforward Amount Remaining
1A	$140,139,000.00	5.7866600000%	5.7866600000%	4.76695645	0.00000000	0.00000000	0.00000000	0.00000014	0.00000000	0.00000000	0.00000000	4.76695659	0.00000000
2A	$408,000,000.00	5.7966600000%	5.7966600000%	4.52806431	0.00000000	0.00000000	0.00000000	0.00000012	0.00000000	0.00000000	0.00000000	4.52806444	0.00000000
2A1A	$165,000,000.00	5.7866600000%	5.7866600000%	4.52025279	0.00000000	0.00000000	0.00000000	0.00000012	0.00000000	0.00000000	0.00000000	4.52025291	0.00000000
2A1B	$55,817,000.00	5.7866600000%	5.7866600000%	4.52025279	0.00000000	0.00000000	0.00000000	0.00000018	0.00000000	0.00000000	0.00000000	4.52025297	0.00000000

Series: WAMU 2007-OA3	Washington Mutual
Issue Date: 03/27/2007
Record Date: 05/31/2007
Distribution Date: 06/25/2007

Interest Factors Report (Continued)
Class	Original Balance	Interest Rate Accrued	Interest Rate Paid	Current Month Interest Accrued	Prepayment Interest Shortfall	Relief Act Interest Shortfall	Other Interest Shortfall	Unscheduled Interest	Interest Reimbursed	Carryforward Amount Paid	Deferred Interest	Total Interest Distribution	Total Carryforward Amount Remaining
CA1B	$96,121,000.00	5.5400000000%	5.5400000000%	4.51630663	0.00000000	0.00000000	0.00000000	0.00000010	0.00000000	0.00000000	0.00000000	4.51630674	0.00000000
CA1B_GRP1	$17,518,000.00	5.5400000000%	5.5400000000%	4.71588709	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	4.71588709	0.00000000
CA1B_GRP2	$78,603,000.00	5.5400000000%	5.5400000000%	4.47182665	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	4.47182665	0.00000000
CA1C	$96,121,000.00	5.6200000000%	5.6200000000%	4.58152402	0.00000000	0.00000000	0.00000000	0.00000010	0.00000000	0.00000000	0.00000000	4.58152412	0.00000000
CA1C_GRP1	$17,518,000.00	5.6200000000%	5.6200000000%	4.78398676	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	4.78398676	0.00000000
CA1C_GRP2	$78,603,000.00	5.6200000000%	5.6200000000%	4.53640179	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	4.53640179	0.00000000
CXPPP	$0.00	0.0000000000%	0.0000000000%	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000
CXPPP_IO_GRP1	$194,639,464.00	0.6658208842%	0.6494107763%	0.54904328	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.53551134	0.00000000
CXPPP_IO_GRP2	$873,359,094.00	0.5938055458%	0.6755373395%	0.46686882	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.53112896	0.00000000
CXPPP_PO_GRP1	$0.00	0.0000000000%	0.0000000000%	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000
CXPPP_PO_GRP2	$0.00	0.0000000000%	0.0000000000%	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000
2X1	$94,334,073.00	1.3755167278%	1.3755167278%	0.59672946	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.59672946	0.00000000
B1	$18,690,000.00	5.7700000000%	5.7700000000%	4.96054789	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	4.96054789	0.00000000

Series: WAMU 2007-OA3	Washington Mutual
Issue Date: 03/27/2007
Record Date: 05/31/2007
Distribution Date: 06/25/2007

Interest Factors Report (Continued)
Class	Original Balance	Interest Rate Accrued	Interest Rate Paid	Current Month Interest Accrued	Prepayment Interest Shortfall	Relief Act Interest Shortfall	Other Interest Shortfall	Unscheduled Interest	Interest Reimbursed	Carryforward Amount Paid	Deferred Interest	Total Interest Distribution	Total Carryforward Amount Remaining
B2	$18,690,000.00	5.8200000000%	5.8200000000%	5.00353344	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	5.00353344	0.00000000
B3	$8,010,000.00	6.0200000000%	6.0200000000%	5.17547690	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	5.17547690	0.00000000
B4	$26,700,000.00	6.2362948152%	6.4199999387%	5.36142809	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.15793371	0.00000000	5.51936180	0.00000000
B5	$11,214,000.00	6.2362948152%	6.5200003352%	5.36142768	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.24390494	0.00000000	5.60533351	0.00000000
B6	$4,806,000.00	6.2362948152%	6.5199996534%	5.36142738	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.24390553	0.00000000	5.60533292	0.00000000
B7	$4,272,000.00	6.2362948152%	6.5199990416%	5.36142790	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.24390449	0.00000000	5.60533240	0.00000000
B8	$3,204,000.00	6.2362948152%	6.5200008568%	5.36142946	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.24390449	0.00000000	5.60533396	0.00000000
B9	$3,204,000.00	6.2362948152%	6.5200008568%	5.36142946	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.24390449	0.00000000	5.60533396	0.00000000
B10	$8,010,458.00	6.2362948152%	6.5200550836%	5.36142877	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.24395234	0.00000000	5.60538112	0.00000000
R	$100.00	0.0000000000%	0.0000000000%	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.30000000	0.00000000
R_SYN	$0.00	0.0000000000%	0.0000000000%	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000
TFEE	$0.00	0.0000000000%	0.0000000000%	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000

Series: WAMU 2007-OA3	Washington Mutual
Issue Date: 03/27/2007
Record Date: 05/31/2007
Distribution Date: 06/25/2007

Collateral Report Pool 8086
LOAN COUNT
Original Loan Count	749
Beginning Loan Count	740
Loans Added	0
Loans Prepaid-in-full	3
Loans Liquidated-in-full	0
Loans Repurchased	0
Ending Loan Count	737
PRINCIPAL BALANCE
Original Scheduled Principal Balance	$194,639,464.48
Beginning Scheduled Principal Balance	$192,602,236.62
Scheduled Principal Received or Advanced	($648,082.45)
Unscheduled Principal	$63,006.44
Prepayments-in-full	$772,284.07

Series: WAMU 2007-OA3	Washington Mutual
Issue Date: 03/27/2007
Record Date: 05/31/2007
Distribution Date: 06/25/2007

Collateral Report Pool 8086 (Continued)
PRINCIPAL BALANCE
Liquidations-in-full	$0.00
Repurchases	$0.00
Principal Losses	$0.00
Ending Scheduled Principal Balance	$192,415,028.56
INTEREST
Accrued Interest at Gross Rate	$1,266,426.01
Unscheduled Interest	$0.14
Uncollected Interest	($66.03)
Relief Act Shortfall	$0.00
Prepayment Interest Shortfall	$0.00
Other Interest Shortfall	$0.00

Series: WAMU 2007-OA3	Washington Mutual
Issue Date: 03/27/2007
Record Date: 05/31/2007
Distribution Date: 06/25/2007

Collateral Report Pool 8086 (Continued)
FEES
Servicing Fees	$223,594.64
Other Fees	$0.00
ADDITIONAL FUNDS
Excess Liquidation Proceeds	$0.00
Subsequent Recoveries	$0.00
Prepayment Penalties	$0.00
Other	$0.00

Series: WAMU 2007-OA3	Washington Mutual
Issue Date: 03/27/2007
Record Date: 05/31/2007
Distribution Date: 06/25/2007

Collateral Report Pool 8087
LOAN COUNT
Original Loan Count	100
Beginning Loan Count	64
Loans Added	0
Loans Prepaid-in-full	11
Loans Liquidated-in-full	0
Loans Repurchased	0
Ending Loan Count	53
PRINCIPAL BALANCE
Original Scheduled Principal Balance	$94,334,073.72
Beginning Scheduled Principal Balance	$49,109,036.48
Scheduled Principal Received or Advanced	($126,595.80)
Unscheduled Principal	$11,618.42
Prepayments-in-full	$10,155,440.57

Series: WAMU 2007-OA3	Washington Mutual
Issue Date: 03/27/2007
Record Date: 05/31/2007
Distribution Date: 06/25/2007

Collateral Report Pool 8087 (Continued)
PRINCIPAL BALANCE
Liquidations-in-full	$0.00
Repurchases	$0.00
Principal Losses	$0.00
Ending Scheduled Principal Balance	$39,068,573.29
INTEREST
Accrued Interest at Gross Rate	$319,865.30
Unscheduled Interest	$0.03
Uncollected Interest	($6,722.79)
Relief Act Shortfall	$0.00
Prepayment Interest Shortfall	$0.00
Other Interest Shortfall	$0.00

Series: WAMU 2007-OA3	Washington Mutual
Issue Date: 03/27/2007
Record Date: 05/31/2007
Distribution Date: 06/25/2007

Collateral Report Pool 8087 (Continued)
FEES
Servicing Fees	$15,346.57
Other Fees	$0.00
ADDITIONAL FUNDS
Excess Liquidation Proceeds	$0.00
Subsequent Recoveries	$0.00
Prepayment Penalties	$0.00
Other	$0.00

Series: WAMU 2007-OA3	Washington Mutual
Issue Date: 03/27/2007
Record Date: 05/31/2007
Distribution Date: 06/25/2007

Collateral Report Pool 8088
LOAN COUNT
Original Loan Count	1057
Beginning Loan Count	1049
Loans Added	0
Loans Prepaid-in-full	9
Loans Liquidated-in-full	0
Loans Repurchased	0
Ending Loan Count	1040
PRINCIPAL BALANCE
Original Scheduled Principal Balance	$779,025,020.58
Beginning Scheduled Principal Balance	$774,886,232.81
Scheduled Principal Received or Advanced	($2,645,315.70)
Unscheduled Principal	$836,395.40
Prepayments-in-full	$6,515,752.73

Series: WAMU 2007-OA3	Washington Mutual
Issue Date: 03/27/2007
Record Date: 05/31/2007
Distribution Date: 06/25/2007

Collateral Report Pool 8088 (Continued)
PRINCIPAL BALANCE
Liquidations-in-full	$0.00
Repurchases	$0.00
Principal Losses	$0.00
Ending Scheduled Principal Balance	$770,179,400.38
INTEREST
Accrued Interest at Gross Rate	$5,021,539.94
Unscheduled Interest	($0.02)
Uncollected Interest	($2,408.23)
Relief Act Shortfall	$0.00
Prepayment Interest Shortfall	$0.00
Other Interest Shortfall	$0.00

Series: WAMU 2007-OA3	Washington Mutual
Issue Date: 03/27/2007
Record Date: 05/31/2007
Distribution Date: 06/25/2007

Collateral Report Pool 8088 (Continued)
FEES
Servicing Fees	$852,928.47
Other Fees	$0.00
ADDITIONAL FUNDS
Excess Liquidation Proceeds	$0.00
Subsequent Recoveries	$0.00
Prepayment Penalties	$66,171.60
Other	$0.00

Series: WAMU 2007-OA3	Washington Mutual
Issue Date: 03/27/2007
Record Date: 05/31/2007
Distribution Date: 06/25/2007

Collateral Report Group 1
LOAN COUNT
Original Loan Count	1906
Beginning Loan Count	1853
Loans Added	0
Loans Prepaid-in-full	23
Loans Liquidated-in-full	0
Loans Repurchased	0
Ending Loan Count	1830
PRINCIPAL BALANCE
Original Scheduled Principal Balance	$1,067,998,558.78
Beginning Scheduled Principal Balance	$1,016,597,505.91
Scheduled Principal Received or Advanced	($3,419,993.95)
Unscheduled Principal	$911,020.26
Prepayments-in-full	$17,443,477.37

Series: WAMU 2007-OA3	Washington Mutual
Issue Date: 03/27/2007
Record Date: 05/31/2007
Distribution Date: 06/25/2007

Collateral Report Group 1 (Continued)
PRINCIPAL BALANCE
Liquidations-in-full	$0.00
Repurchases	$0.00
Principal Losses	$0.00
Ending Scheduled Principal Balance	$1,001,663,002.23
INTEREST
Accrued Interest at Gross Rate	$6,607,831.25
Unscheduled Interest	$0.15
Uncollected Interest	($9,197.05)
Relief Act Shortfall	$0.00
Prepayment Interest Shortfall	$0.00
Other Interest Shortfall	$0.00

Series: WAMU 2007-OA3	Washington Mutual
Issue Date: 03/27/2007
Record Date: 05/31/2007
Distribution Date: 06/25/2007

Collateral Report Group 1 (Continued)
FEES
Servicing Fees	$1,091,869.68
Other Fees	$0.00
ADDITIONAL FUNDS
Excess Liquidation Proceeds	$0.00
Subsequent Recoveries	$0.00
Prepayment Penalties	$66,171.60
Other	$0.00

Series: WAMU 2007-OA3	Washington Mutual
Issue Date: 03/27/2007
Record Date: 05/31/2007
Distribution Date: 06/25/2007

Collateral Report Total
LOAN COUNT
Original Loan Count	1906
Beginning Loan Count	1853
Loans Added	0
Loans Prepaid-in-full	23
Loans Liquidated-in-full	0
Loans Repurchased	0
Ending Loan Count	1830
PRINCIPAL BALANCE
Original Scheduled Principal Balance	$1,067,998,558.78
Beginning Scheduled Principal Balance	$1,016,597,505.91
Scheduled Principal Received or Advanced	($3,419,993.95)
Unscheduled Principal	$911,020.26
Prepayments-in-full	$17,443,477.37

Series: WAMU 2007-OA3	Washington Mutual
Issue Date: 03/27/2007
Record Date: 05/31/2007
Distribution Date: 06/25/2007

Collateral Report Total (Continued)
PRINCIPAL BALANCE
Liquidations-in-full	$0.00
Repurchases	$0.00
Principal Losses	$0.00
Ending Scheduled Principal Balance	$1,001,663,002.23
INTEREST
Accrued Interest at Gross Rate	$6,607,831.25
Unscheduled Interest	$0.15
Uncollected Interest	($9,197.05)
Relief Act Shortfall	$0.00
Prepayment Interest Shortfall	$0.00
Other Interest Shortfall	$0.00

Series: WAMU 2007-OA3	Washington Mutual
Issue Date: 03/27/2007
Record Date: 05/31/2007
Distribution Date: 06/25/2007

Collateral Report Total (Continued)
FEES
Servicing Fees	$1,091,869.68
Other Fees	$0.00
ADDITIONAL FUNDS
Excess Liquidation Proceeds	$0.00
Subsequent Recoveries	$0.00
Prepayment Penalties	$66,171.60
Other	$0.00

Series: WAMU 2007-OA3	Washington Mutual
Issue Date: 03/27/2007
Record Date: 05/31/2007
Distribution Date: 06/25/2007

Delinquency Information by Group*
Group ID	1 Month Count	Scheduled Ending Balance	2 Months Count	Scheduled Ending Balance	3 Months Count	Scheduled Ending Balance	4+ Months Count	Scheduled Ending Balance
Pool 8086	8	$1,915,591.46	3	$1,049,824.03	0	$0.00	0	$0.00
Pool 8087	1	$82,066.63	0	$0.00	0	$0.00	0	$0.00
Pool 8088	21	$14,725,232.93	4	$1,644,363.44	1	$428,288.07	0	$0.00
Group 1	30	$16,722,891.02	7	$2,694,187.47	1	$428,288.07	0	$0.00
Aggregate	30	$16,722,891.02	7	$2,694,187.47	1	$428,288.07	0	$0.00

* Does not include mortgage loans in foreclosure or REO.

Series: WAMU 2007-OA3	Washington Mutual
Issue Date: 03/27/2007
Record Date: 05/31/2007
Distribution Date: 06/25/2007

Foreclosure, REO, and Bankruptcy by Group**
Group ID	Foreclosure Count	Scheduled Ending Balance	REO Count	Scheduled Ending Balance	Bankruptcy Count	Scheduled Ending Balance
Pool 8086	0	$0.00	0	$0.00	0	$0.00
Pool 8087	0	$0.00	0	$0.00	0	$0.00
Pool 8088	0	$0.00	0	$0.00	0	$0.00
Group 1	0	$0.00	0	$0.00	0	$0.00
Aggregate	0	$0.00	0	$0.00	0	$0.00

** Loans in Bankruptcy will also be reflected under their applicable delinquency or foreclosure status.

Series: WAMU 2007-OA3	Washington Mutual
Issue Date: 03/27/2007
Record Date: 05/31/2007
Distribution Date: 06/25/2007

Aggregate Loss Amount by Group
Group ID	Count	Loss Amount
Pool 8086	0	$0.00
Pool 8087	0	$0.00
Pool 8088	0	$0.00
Group 1	0	$0.00
Aggregate	0	$0.00

Servicer Advances by Group
Group	Count	Total
Pool 8086	586	$321,768.66
Pool 8087	48	$134,272.77
Pool 8088	841	$1,250,367.34
Group 1	1475	$1,706,408.77
Aggregate	1475	$1,706,408.77

Series: WAMU 2007-OA3	Washington Mutual
Issue Date: 03/27/2007
Record Date: 05/31/2007
Distribution Date: 06/25/2007

Stop Advances Loans
Group	Count	Loan Balance	Total Scheduled P&I
Pool 8086	0	$0.00	$0.00
Pool 8087	0	$0.00	$0.00
Pool 8088	0	$0.00	$0.00
Group 1	0	$0.00	$0.00
Aggregate	0	$0.00	$0.00

Series: WAMU 2007-OA3	Washington Mutual
Issue Date: 03/27/2007
Record Date: 05/31/2007
Distribution Date: 06/25/2007

Delinquency Roll Rates-Aggregate***
Current Value	Current		1 Month		2 Months		3 Months
Prior Value	Count	Balance	Count	Balance	Count	Balance	Count	Balance
Current	1757	$957,797,126.46	26	$14,430,409.69	1	$424,238.02	1	$428,288.07
Delq 1 Month	35	$24,020,509.21	4	$2,292,481.33	6	$2,269,949.45	0	$0.00
Delq 2 Month	0	$0.00	0	$0.00	0	$0.00	0	$0.00
Delq 3 Month	0	$0.00	0	$0.00	0	$0.00	0	$0.00
Delq 4 Month	0	$0.00	0	$0.00	0	$0.00	0	$0.00
Foreclosure	0	$0.00	0	$0.00	0	$0.00	0	$0.00

Current Value	4+ Months		Foreclosure		REO
Prior Value	Count	Balance	Count	Balance	Count	Balance
Current	0	$0.00	0	$0.00	0	$0.00
Delq 1 Month	0	$0.00	0	$0.00	0	$0.00
Delq 2 Month	0	$0.00	0	$0.00	0	$0.00
Delq 3 Month	0	$0.00	0	$0.00	0	$0.00
Delq 4 Month	0	$0.00	0	$0.00	0	$0.00
Foreclosure	0	$0.00	0	$0.00	0	$0.00

*** To use this chart, locate along the Current Value row the desired delinquency status as of the immediately preceding due date (e.g. Current, 1 Month delinquent, etc.). Use the left hand column labeled Prior Value to see the prior month's value. Follow the selected Current Value column to the desired Prior Value row.

Series: WAMU 2007-OA3	Washington Mutual
Issue Date: 03/27/2007
Record Date: 05/31/2007
Distribution Date: 06/25/2007

Credit Enhancement
Type	Original Balance	Beginning Balance	Reduction	Increase	Ending Balance
Interest Coverage Account	$3,633,433.42	$0.00	$0.00	$0.00	$0.00
Over Collateralization	$0.00	$0.00	$0.00	$0.00	$0.00
Reserve Account	$0.00	$0.00	$0.00	$0.00	$0.00
Other	$0.00	$0.00	$0.00	$0.00	$0.00

Insurance
Insurance Type	Original Balance	Claims Paid	Coverage Remaining
Pool Insurance	$0.00	$0.00	$0.00
Other	$0.00	$0.00	$0.00

Series: WAMU 2007-OA3	Washington Mutual
Issue Date: 03/27/2007
Record Date: 05/31/2007
Distribution Date: 06/25/2007

Subordinate Class Certificate Balances
The Class Principal Balances of each Class of the Class B1,B2,B3,B4,B5,B6,B7,B8,B9,B10 Certificates immediately after the principal and interest distribution on 06/25/2007 are as follows:
Class	Ending Principal Balance	Percentage of Aggregate Certificate Principal Balance on Closing Date	Percentage of Aggregate Certificate Ending Principal Balance
B1	$18,659,553.21	1.75%	1.86%
B2	$18,659,553.21	1.75%	1.86%
B3	$7,996,951.37	0.75%	0.80%
B4	$26,656,504.58	2.50%	2.66%
B5	$11,195,731.93	1.05%	1.12%
B6	$4,798,170.82	0.45%	0.48%
B7	$4,265,040.73	0.40%	0.43%
B8	$3,198,780.55	0.30%	0.32%
B9	$3,198,780.55	0.30%	0.32%
B10	$7,997,409.40	0.75%	0.80%
Total	$106,626,476.35	10.00%	10.64%

Series: WAMU 2007-OA3	Washington Mutual
Issue Date: 03/27/2007
Record Date: 05/31/2007
Distribution Date: 06/25/2007

Glossary of Terms
TERM	DEFINITION
Average Ending Scheduled Principal Balance	Average scheduled principal balance of all mortgage loans as of the immediately preceding due date.
Compensating Interest	Interest paid by the servicer or master servicer in respect of Prepayment Interest Shortfall, subject to specified caps.
CPR (Constant Prepayment Rate)	The annualized, compounded single month mortality rate.
Current Interest Accrued	The interest accrued for the current month's distribution.
Deferred Interest	When a scheduled monthly payment is less than required to satisfy the note rate, the unpaid interest is deferred by adding it to the loan balance and the certificate balances.
Excess Liquidation Proceeds	Funds received at the time of liquidation in excess of the amount needed to satisfy the outstanding scheduled principal balance and related expenses.
Interest Rate Accrued	The rate at which interest is accrued for the current month's distribution.
Interest Rate Paid	The rate at which interest is paid for the current month's distribution.
Uncollected Interest	Interest not collected on delinquent loans for which scheduled payments are no longer being advanced, interest uncollected on prepayments and interest uncollected on liquidations.
Other Interest Shortfall	Any interest shortfall other than Uncompensated Interest Shortfall, Deferred Interest or Interest Uncollected on Non-Earning Assets.
Over Collateralization	Any excess of the aggregate principal balance of the mortgage loans over the aggregate principal balance of the certificates.
Prefunding Amount	The amount of cash being held for future loan purchases.

Series: WAMU 2007-OA3	Washington Mutual
Issue Date: 03/27/2007
Record Date: 05/31/2007
Distribution Date: 06/25/2007

Glossary of Terms (Continued)
TERM	DEFINITION
Prepayment Interest Shortfall	Any shortfall in collections of interest on mortgage loans resulting from prepayments in full or partial prepayments.
Principal Loss	The amount of principal reduction due to a loss realized on the mortgage loans.
Principal Reimbursed	The amount of principal passed through as a reimbursement.
PSA (Prepayment Speed Assumption)	A prepayment model that in its base case (stated as 100% PSA), assumes that prepayments start in month one at an annual CPR of 0.2%, rising linearly to 6.0% CPR in month 30, and then remain flat at 6.0% CPR thereafter.
Relief Act Shortfall	Interest shortfall resulting from application of the Servicemembers Civil Relief Act.
REO (Real Estate Owned)	Property acquired by the trust through foreclosure or deed-in-lieu of foreclosure on a defaulted loan.
Reserve Account	Funded or non-funded accounts set up at either the property or portfolio level in in anticipation of periodic or non-periodic capital expenditures or cash needs.
Servicer Advances	Scheduled principal and interest advances made by the servicer or master servicer for delinquent mortgage loans.
Servicing Fees	The monthly fee paid to the servicer to perform primary servicing function for the master servicer with respect to the mortgage loans and if applicable the fee charged by the master servicer for supervising the mortgage loan servicing.
SMM (Single Month Mortality)	In any given month, the SMM measures the percentage of the beginning pool balance that was paid back earlier than scheduled through payoffs.
Stop Advance	The amount of principal and interest on delinquent mortgage loans for which scheduled payments are no longer being advanced.
Subsequent Recoveries	The amount of funds recovered on mortgage loans that were previously liquidated at a loss.
Trigger Event	An event that may require a change in payment priority.

Series: WAMU 2007-OA3	Washington Mutual
Issue Date: 03/27/2007
Record Date: 05/31/2007
Distribution Date: 06/25/2007

Glossary of Terms (Continued)
TERM	DEFINITION
Unscheduled Interest	Interested collected in addition to the scheduled interest payment.
Unscheduled Principal	Payments of principal which were received with respect to any mortgage loan during the prior period, other than monthly scheduled principal, prepayments in full, repurchases, liquidation principal and subsequent recoveries.
Weighted Average Loan Age	For any distribution date, the weighted average of the loan age on the mortgage loans as of the immediately preceding due date.
Weighted Average Mortgage Interest Rate	For any distribution date, the weighted average of the mortgage interest rates on the mortgage loans as of the second preceding due date (after giving effect to the payments due on the mortgage loans on that due date).
Weighted Average Pass Through Rate	For any distribution date, the weighted average of the pass-through rates on the mortgage loans as of the second preceding due date (after giving effect to the payments due on the mortgage loans on that due date).
Weighted Average Remaining Term	For any distribution date, the weighted average of the maturity on the mortgage loans as of the immediately preceding due date.
MBA Delinquency Calculation	In this calculation, a loan increases its delinquency status if a monthly payment is not received by the end of the day immediately preceding the loan's next due date.
OTS Delinquency Calculation	In this calculation, a loan increases its delinquency status if a monthly payment is not received by the loan's due date in the following month.

WaMu Mortgage Pass-Through Certificates, Series 2007-OA3 10-D