8-K

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of

the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported):

August 11, 2009

COLUMBIA BANKING SYSTEM, INC.

(Exact name of registrant as specified in its charter)

Washington

(State or other jurisdiction of incorporation)

0-20288	91-1422237
(Commission File Number)	IRS Employer Identification No.

1301 A Street

Tacoma, WA 98402

(Address of principal executive offices) (zip code)

Registrant’s telephone number, including area code: (253) 305-1900

(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 obligations of the registrant under any of the following provisions:

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

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

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

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

Item 7.01 Regulation FD Disclosure

On August 11, 2009, Columbia Banking System, Inc. (the “Company”) announced that it raised approximately $120 million through a previously announced public offering by issuing 9,775,000 shares of the Company’s common stock, including 1,275,000 shares pursuant to the underwriters’ over-allotment option, at a price of $12.25 per share. The net proceeds to the Company after deducting underwriting discounts and commissions and estimated offering expenses are expected to be approximately $113.8 million. Keefe, Bruyette & Woods, Inc. acted as lead book-running manager of the offering, with D.A. Davidson & Co. as a co-manager.

In accordance with General Instruction B.2. of Form 8-K, the information in Item 7.01 and the press release shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section, nor shall such information and exhibit be deemed incorporated by reference into any filing under the Securities Act or the Exchange Act, except as shall be expressly set forth by specific reference in such a filing.

Item 9.01. Financial Statements and Exhibits.

(a) Financial Statements: None

(b) Pro Forma Financial Information: None

(c) Shell Company Transactions: None

(d) Exhibits.

99.1 Press Release dated August 11, 2009, announcing the exercise of the over-allotment and settlement of the offering.

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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.

Dated: August 11, 2009	COLUMBIA BANKING SYSTEM, INC.
	By:	/s/    Melanie J. Dressel
		Melanie J. Dressel
		President and Chief Executive Officer

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EX-99.1

Exhibit 99.1

FOR IMMEDIATE RELEASE

August 11, 2009

Contacts:    Melanie J. Dressel, President and

Chief Executive Officer

(253) 305-1911

Gary R. Schminkey, Executive Vice President

and Chief Financial Officer

(253) 305-1966

COLUMBIA BANKING SYSTEM ANNOUNCES

CLOSING OF $120 MILLION COMMON STOCK OFFERING, INCLUDING THE

EXERCISE OF THE UNDERWRITERS’ OVER-ALLOTMENT OPTION

TACOMA, Washington, August 11, 2009 — Columbia Banking System, Inc. (NASDAQ: COLB) announced that they have raised $120 million through the previously announced public offering by issuing 9,775,000 shares of the Company’s common stock, including 1,275,000 shares pursuant to the underwriters’ over-allotment option, at a price of $12.25 per share. The net proceeds to the Company after deducting underwriting discounts and commissions and estimated offering expenses are expected to be approximately $113.8 million. Keefe, Bruyette & Woods, Inc. acted as lead book-running manager of the offering, with D.A. Davidson & Co. as a co-manager.

“We are extremely pleased with the results of our public offering, which validates the strength of our franchise,” said Melanie Dressel, President and Chief Executive Officer. “This additional capital, when added to our already strong capital levels, gives us the flexibility to respond quickly and effectively to business opportunities as they arise.”

This announcement shall not constitute an offer to sell or the solicitation of an offer to buy these securities, nor shall there be any offer or sale of these securities in any jurisdiction in which such offer, solicitation or sale would be unlawful. The registration statement relating to the common stock has been filed with the Securities and Exchange Commission and is effective. A prospectus supplement and accompanying prospectus may be obtained from Keefe, Bruyette & Woods, Inc., Equity Capital Markets, 787 Seventh Avenue, 4th Floor, New York, NY 10019, or by calling toll-free (800) 966-1559 or from D.A. Davidson & Co., Equity Capital Markets, 8 Third Street North, Great Falls, MT 59401 or by calling toll-free (800) 332-5915.

About Columbia

Headquartered in Tacoma, Washington, Columbia Banking System, Inc. is the holding company of Columbia State Bank, a Washington state-chartered full-service commercial bank which was awarded second place in the large employer category by Seattle Business Magazine’s “100 Best Companies to Work For” for 2009. With the 2007 acquisitions of Mountain Bank Holding Company and Town Center Bancorp and the 2008 internal merger of its subsidiary, Bank of Astoria, into Columbia State Bank, Columbia Banking System has 51 banking offices in Pierce, King, Cowlitz, Kitsap, Thurston and Whatcom counties in Washington State, and Clackamas, Clatsop, Tillamook and Multnomah counties in Oregon. Included in Columbia State Bank are former branches of Mt. Rainier National Bank, doing business as Mt. Rainier Bank, with 5 branches in King and Pierce counties. Columbia State Bank does business under the Bank of Astoria name at the Bank of Astoria’s former branches located in Astoria, Warrenton, Seaside and Cannon Beach in Clatsop County and in Manzanita and Tillamook in Tillamook County. More information about Columbia can be found on its website at www.columbiabank.com.

Note Regarding Forward-Looking Statements

This news release includes forward-looking statements. These forward looking statements describe management’s expectations regarding future events and developments such as our offering of common stock and the use of any proceeds from that offering. The words “will,” “believe,” “expect,” “should,” and “anticipate” and words of similar construction are intended in part to help identify forward-looking statements. Future events are difficult to predict, and the expectations described above are necessarily subject to risk and uncertainty that may cause actual results to differ materially and adversely. In addition to discussions about risks and uncertainties set forth from time to time in our filings with the SEC, factors that may cause actual results to differ materially from those contemplated by such forward-looking statements include, among others, the following possibilities: (1) local and national economic conditions are less favorable than expected or have a more direct and pronounced effect on us than expected and adversely affect our ability to continue internal growth at historical rates and maintain the quality of our earning assets; (2) a continued decline in the housing/real estate market; (3) changes in interest rates significantly reduce interest margins and negatively affect funding sources; (4) deterioration of credit quality that could, among other things, increase defaults and delinquency risks in the loan portfolios; (5) projected business increases following strategic expansion activities are lower than expected; (6) competitive pressure among financial institutions increases significantly; (7) legislation or regulatory requirements or changes adversely affect the businesses in which we are engaged; and (8) our ability to realize the efficiencies we expect to receive from our investments in personnel, acquisitions and infrastructure.

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