~~UNITED~~SECURITIES ~~STATES~~AND EXCHANGE COMMISSION Washington, D.C. 20549

~~SECURITIES~~FORM ~~AND~~8-K CURRENT ~~EXCHANGE COMMISSION~~REPORT

Washington, D.C. 20549

Form 8-K

Current Report

Pursuant to Section 13 or 15(d) of the
Securities Exchange Act of 1934

~~Date~~April 26, 2007Date of Report (~~Date~~date of earliest event reported)~~: April 25, 2007~~

~~WaMu~~WAMU ~~Mortgage~~ASSET ~~Pass-Through~~ACCEPTANCE ~~Certificates, Series 2007-OA4 Issuing Entity~~ CORP.

~~WAMU~~as ~~ASSET~~Depositor ~~ACCEPTANCE~~under ~~CORP.~~a Pooling and Servicing Agreement dated as of April 1, 2007 providing for the issuance of ~~Depositor~~WaMu MORTGAGE PASS-THROUGH CERTIFICATES SERIES 2007-OA4 TRUST(Exact name of ~~registrant~~Registrant as specified in its charter)

WASHINGTON MUTUAL BANK Sponsor

Delaware		333-141255		20-2258610
(State or other jurisdiction of incorporation)		(Commission File Number)		(I.R.S. Employer Identification No.)

333-141255-02

(Commission File Number)

Delaware		20-2258610
(State or other jurisdiction of incorporation)		(I.R.S. Employer Identification No.)

1301 SECOND AVENUE, WMC 3501A
SEATTLE, WASHINGTON 98101
(Address of principal executive offices and Zip Code)

Registrant's telephone number, including area code: (206) 500-4418

(Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions ~~(see General Instruction A.2. below)~~:

o Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

o Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

o Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

o Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

SECTION ~~6 ASSET-BACKED~~9 ~~SECURITIES~~ FINANCIAL STATEMENTS AND EXHIBITS

Item 69.01. ~~ABS~~Financial ~~Informational~~Statements and ~~Computational Material~~Exhibits.

~~ABS informational and computational material for the depositor and/or sponsor consisting of certain loan information is provided on the following exhibit attached to this Form 8-K:~~(d) Exhibits

Exhibit Number		Description
99.1		Certain information concerning the mortgage loans prepared in connection with the Registrant's WaMu Mortgage Pass-Through Certificates, Series 2007-OA4

The following exhibits are filed herewith:

4.1	Pooling and Servicing Agreement by and among WaMu Asset Acceptance Corp., as Depositor, Washington Mutual Bank, as Servicer, LaSalle Bank National Association, as Trustee, and Christiana Bank & Trust Company, as Delaware Trustee, dated as of April 1, 2007.

4.2

Mortgage Loan Purchase Agreement, dated as of October 25, 2005, among WaMu Asset Acceptance Corp., Washington Mutual Bank and Washington Mutual Bank fsb (incorporated herein by reference from Exhibit 4.6 to the Current Report on Form 8-K filed by WaMu Asset Acceptance Corp. on November 8, 2005 with respect to Registration Statement No. 333-123034).

4.3

Amended and Restated Administrative Agent Agreement, dated as of February 1, 2005, between Washington Mutual Bank and Washington Mutual Mortgage Securities Corp. (incorporated herein by reference from Exhibit 4.9 to the Current Report on Form 8-K filed by WaMu Asset Acceptance Corp. on March 6, 2006 with respect to Registration Statement No. 333-130795).

99.1

Excerpt from Section 2 of the Term Sheet dated April 26, 2007 between Washington Mutual Bank, as seller, and WaMu Asset Acceptance Corp., as purchaser. For a form of term sheet, see Exhibit B to Exhibit 4.6 to to the Current Report on Form 8-K filed by WaMu Asset Acceptance Corp. on November 8, 2005 with respect to Registration Statement No. 333-123034.

99.2	Novation confirmation regarding interest rate cap transaction, dated as of April 26, 2007, among The Bank of New York, Washington Mutual Bank and LaSalle Bank National Association, as trustee on behalf of the trust.

The Mortgage Loan Schedule, included as Exhibit D to the Pooling and Servicing Agreement, has been intentionally omitted from this filing. Copies may be obtained from Washington Mutual Mortgage Securities Corp. or LaSalle Bank National Association by contacting:

in the case of Washington Mutual Mortgage Securities Corp.,

        John Ganzer
        Washington Mutual Mortgage Securities Corp.
        75 N. Fairway Drive,VHF2A01
        Vernon Hills, IL 60061
        Telephone: (847) 549-3113
        Facsimile:     (847) 549-3680

in the case of LaSalle Bank National Association,

        Stefanie Edwards
        LaSalle Bank National Association
        135 S. LaSalle Street, Suite 1511
        Chicago, IL 60603
        Telephone:  (312) 904-8975
        Facsimile:    (312) 904-2084

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

		WAMU ASSET ACCEPTANCE CORP.
Date: April 25, 2007	By:	/s/ Richard Careaga Richard Careaga First Vice President (Authorized Officer)
Date: May 11, 2007	By:	/s/ Richard CareagaRichard Careaga First Vice President (Authorized Officer)

~~EXHIBIT~~Exhibit ~~INDEX~~Index

Exhibit Number		Description
99.1		Certain information concerning the mortgage loans prepared in connection with the Registrant's WaMu Mortgage Pass-Through Certificates, Series 2007-OA4

4.1	Pooling and Servicing Agreement by and among WaMu Asset Acceptance Corp., as Depositor, Washington Mutual Bank, as Servicer, LaSalle Bank National Association, as Trustee, and Christiana Bank & Trust Company, as Delaware Trustee, dated as of April 1, 2007.

4.2

4.3

99.1

99.2	Novation confirmation regarding interest rate cap transaction, dated as of April 26, 2007, among The Bank of New York, Washington Mutual Bank and LaSalle Bank National Association, as trustee on behalf of the trust.

Filing Compare · WaMu Mortgage Pass-Through Certificates, Series 2007-OA4