COLUMBIA BANKING SYSTEM, INC. (NASDAQ:COLB) Files An 8-K Submission of Matters to a Vote of Security Holders

Item5.07.

On June8, 2017, Columbia Banking System, Inc. (Columbia)
held a special meeting of shareholders (the Special
Meeting). At the close of business on April12, 2017, the
record date of the Special Meeting, there were 58,328,142
Columbia common shares issued and outstanding. 51,184,683
Columbia common shares, representing 87.75% of the total Columbia
common shares issued and outstanding were represented in person
or by proxy at the Special Meeting.

At the Special Meeting, holders of Columbia common shares voted
upon: (1)the issuance of Columbia common shares in the merger of
a to-be-formed wholly owned subsidiary of Columbia with and into
Pacific Continental Corporation, an Oregon corporation (the
Columbia Share Issuance Proposal); and (2)the approval of
one or more adjournments of the Special Meeting, if necessary or
appropriate, including adjournments to solicit additional proxies
in favor of the Columbia Share Issuance Proposal (the Columbia
Adjournment Proposal). The final voting results for each of
the proposals voted upon at the Special Meeting, as certified by
the inspector of election, are set forth below. The proposals are
described in further detail in the definitive joint proxy
statement/prospectus for the Special Meeting filed with the
Securities and Exchange Commission on April24, 2017.

Proposal 1: Columbias shareholders approved the
Columbia Share Issuance Proposal. The table below sets forth the
voting results.

Proposal 2: Columbias shareholders approved the
Columbia Adjournment Proposal. The table below sets forth the
voting results.

On June8, 2017, Columbia issued a press release announcing the
results of the Special Meeting. A copy of the press release is
attached hereto as Exhibit 99.1 and is incorporated by reference
herein.

(d) Exhibits.

The following exhibits are being filed herewith:

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About COLUMBIA BANKING SYSTEM, INC. (NASDAQ:COLB)

Columbia Banking System, Inc. is a bank holding company of Columbia State Bank (the Bank) and West Coast Trust Company, Inc. The Company provides a range of banking services to small and medium-sized businesses, professionals and individuals throughout Washington, Oregon and Idaho. The Bank provides a range of financial services through approximately 150 branch locations in Washington, Oregon and Idaho. The Company’s products and services include personal banking, business banking and wealth management. It offers its personal banking customers a range of account products, including noninterest and interest-bearing checking, savings, money market and certificate of deposit accounts. The Company offers its business banking customers with a range of checking, savings, interest bearing money market and certificate of deposit accounts. It provides individual and business retirement solutions, insurance solutions, wealth management and financial planning.