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Exhibit 99

Southwest Bancorp Inc. Reports Net Income

of $5.2 Million for the First Quarter of 2012

April 18, 2012, Stillwater, Oklahoma . . . . Southwest Bancorp, Inc. (NASDAQ Global Select Market - OKSB, OKSBP), (“Southwest”), today reported earnings for the first quarter of 2012 of $5.2 million, compared to $2.5 million for the first quarter of 2011. Net income available to common shareholders was $4.1 million, or $0.21 per diluted share for the first quarter of 2012, compared to $1.4 million, or $0.07 per diluted share for the first quarter of 2011. The increase in quarterly income over the first quarter of 2011 was primarily the result of a lower required provision for loan losses and reduced noninterest expense, offset in part by a loan volume-driven decrease in net interest income. Southwest recorded a net loss of ($58.3) million and a net loss available to common shareholders of ($59.3) million, or ($3.05) per diluted share, for the fourth quarter of 2011.

“We are pleased with the first quarter earnings and quarter-end credit quality.” Rick Green, President and CEO, stated. “These positive outcomes are mainly attributable to the changes we made last spring in our credit and lending functions and our fourth quarter 2011 sales of loans and other real estate.” In the fourth quarter of 2011, Southwest sold approximately $300 million of loans and other real estate. Approximately $170 million of the total were nonperforming assets. The remaining assets sold were classified worse than “pass” in Southwest’s credit risk system or were pass assets related to other assets sold. These sales contributed to last year’s loss, but immediately and substantially reduced Southwest’s nonperforming assets and potential problem loans.

Mr. Green stated, “At quarter-end, our levels of nonperforming assets and potential problem loans were essentially the same as at year-end 2011, and our allowance for loan losses at quarter-end stood at over 300% of nonperforming loans.

“Our total portfolio loans continued to decrease in the quarter, as we had anticipated. The lower volume led to lower net interest income. The first quarter decrease is a result of ordinary payoffs and softness in loan demand. We plan to stabilize loan revenue and volume by generating new loans prudently and profitably, but currently expect continued volume declines until later this year.

“As of March 31, 2012, the capital ratios for Southwest and each of its banking subsidiaries continued to substantially exceed the ratios for regulatory classification as “well-capitalized”.

“Our first quarter 2012 produced a reasonable profit from solid core banking. Your Board of Directors and Management are driven to return to sustained profitability, the resumption of dividends for trust preferred securities, preferred stock, and common stock, and to once again produce reliable and attractive returns for our shareholders.”

Key items for the quarter were as follows:

Unless otherwise indicated, the following discussion excludes “covered” assets, which are subject to loss sharing agreements with the FDIC. For information on covered versus noncovered assets, please see the accompanying unaudited financial statements and tables.

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Southwest Bancorp Inc. Reports Net Income of $5.2 Million for the First Quarter of 2012

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Southwest Bancorp Inc. Reports Net Income of $5.2 Million for the First Quarter of 2012

Financial Overview

Condition: Total assets were $2.3 billion and total loans were $1.6 billion at March 31, 2012, decreases of 5% and 7%, respectively, from December 31, 2011.

At March 31, 2012 the allowance for loan losses was $45.1 million, an increase of 1% from December 31, 2011.

Total core funding, which includes all non-brokered deposits and sweep repurchase agreements, comprised 98% of total funding as of March 31, 2012, compared to 94% at December 31, 2011. Core funding by segment is as follows as of March 31, 2012 and December 31, 2011, respectively: $1,386.1 million and $1,426.2 million in Oklahoma banking, $152.1 million and $156.2 million in Texas banking, $265.3 million and $273.6 million in Kansas banking, and $13.6 million and $3.9 million in the secondary market and other operations segments. Wholesale funding, including FHLB borrowings, federal funds purchased, and brokered deposits, accounted for 2% of total funding at March 31, 2012, compared to 6% at December 31, 2011. Please see Table 6 for details on these non-GAAP financial measures.

First Quarter Results:

Summary: Net income available to common shareholders was $4.1 million as of March 31, 2012, compared to $1.4 million as of March 31, 2011. The $2.7 million increase in our net income available to common shareholders from 2011 is the result of a $7.3 million decrease in the provision for loan losses, a $1.3 million decrease in noninterest expense, and a $0.3 million increase in noninterest income, offset in part by a $4.6 million decrease in net interest income and a $1.6 million increase in income tax expense.

The first quarter 2012 effective tax rate was 37.50%.

Net Interest Income: Net interest income totaled $20.9 million for the first quarter of 2012, compared to $25.4 million for the first quarter of 2011, a decrease of $4.6 million, or 18%, and to $21.9 million for the fourth quarter of 2011, a decrease of $1.0 million, or 5%. Net interest margin was 3.83% for the first quarter of 2012, compared to 3.78% for the first quarter of 2011 and 3.62% for the fourth quarter of 2011. Included in the first quarter of 2012 and the first quarter of 2011 net interest margins were immaterial adjustments of the discount accretion on loans and the loss share receivable, offset by immaterial interest reversals on nonaccrual loans. Included in the fourth quarter of 2011 was a net reduction of $1.2 million resulting from interest reversals on nonaccrual loans, offset by quarterly adjustments of the discount accretion on loans and the loss share receivable. The net effects of these adjustments on net interest margin were a 1 basis point increase for the first quarter of 2012, a 1 basis point increase for the first quarter of 2011, and a 19 basis point decrease for the fourth quarter of 2011.

Provision for Loan Losses and Net Charge Offs: The provision for loan losses totaled $1.7 million for the first quarter of 2012, compared to $9.1 million for first quarter of 2011 and $78.3 million for the fourth quarter of 2011. Net charge-offs totaled $1.3 million, or 0.32% (annualized) of average portfolio loans for the first quarter of 2012, compared to $13.0 million, or 2.25% (annualized) of average portfolio loans for the first quarter of 2011 and $98.3 million, or 19.78% (annualized) of average portfolio loans for the fourth quarter of 2011.

Noninterest Income: Noninterest income totaled $3.5 million for the first quarter of 2012, compared to $3.2 million for the first quarter of 2011 and $3.6 million for the fourth quarter of 2011. The increase from first quarter of 2011 in noninterest income was primarily the result of a $0.3 million increase in the gain on sale of loans, offset in part by a $0.1 million decrease in other noninterest income, which includes the withdrawal from investments that took place in first quarter of 2011.

Noninterest Expense: Noninterest expense totaled $14.3 million for the first quarter of 2012, compared to $15.6 million for the first quarter 2011 and $41.9 million for the fourth quarter of 2011. The decrease from first quarter of 2011 consists of: a $0.5 million decrease in FDIC and other insurance expense as a result of the change in premium calculation methodology from a deposit basis to an asset basis; a $0.4 million decrease in general and administrative expense, which is the result of reduced legal fees and no remaining obligation to accrue for estimated interest and penalties on unrecognized tax benefits; a $0.3 million decrease in personnel expense, primarily as a result of decreased profit sharing contributions; and a $0.3 million decrease in occupancy expense, due to decreased building rental expense, maintenance renewal expense, and depreciation expense as a result of controlling capital expenditures; offset in part by a $0.1 million increase in the provision for unfunded loan commitments.

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Southwest Bancorp Inc. Reports Net Income of $5.2 Million for the First Quarter of 2012

Southwest Bancorp and Subsidiaries

Southwest is the bank holding company for Stillwater National Bank and Trust Company (“Stillwater National”) and Bank of Kansas. Through its subsidiaries, Southwest offers commercial and consumer lending, deposit and investment services, specialized cash management, and other financial services from offices in Oklahoma, Texas, and Kansas, and on the Internet, through SNB DirectBanker^®. We were organized in 1981 as the holding company for Stillwater National, which was chartered in 1894. At March 31, 2012 we had total assets of $2.3 billion, deposits of $1.8 billion, and shareholders’ equity of $311.6 million.

Our area of expertise focuses on the special financial needs of healthcare and health professionals, businesses and their managers and owners, and commercial and commercial real estate borrowers. We established a strategic focus on healthcare lending in 1974. We provide credit and other services, such as deposits, cash management, and document imaging for physicians and other healthcare practitioners to start or develop their practices and finance the development and purchase of medical offices, clinics, surgical care centers, hospitals, and similar facilities. As of March 31, 2012, approximately $562.5 million, or 35%, of our noncovered loans were loans to individuals and businesses in the healthcare industry. We conduct regular market reviews of our current and potential healthcare lending and the appropriate concentrations within healthcare based upon economic and regulatory conditions.

We also focus on commercial real estate mortgage and construction credits. We do not focus on one-to-four family residential development loans or “spec” residential property credits. Additionally, subprime residential lending has never been a part of our business strategy, and our exposure to subprime mortgage loans and subprime lenders is minimal. One-to-four family mortgages account for less than 5% of total noncovered loans. As of March 31, 2012 approximately $1.2 billion, or 76%, of our noncovered loans were commercial real estate mortgage and construction loans, including $376.8 million of loans to individuals and businesses in the healthcare industry.

Southwest’s common stock is traded on the NASDAQ Global Select Market under the symbol OKSB. Southwest’s public trust preferred securities are traded on the NASDAQ Global Select Market under the symbol OKSBP.

Caution About Forward-Looking Statements

We make forward-looking statements in this news release that are subject to risks and uncertainties. We intend these statements to be covered by the safe harbor provision for forward-looking statements contained in the Private Securities Litigation Reform Act of 1995.

These forward-looking statements include:

These forward-looking statements are subject to significant uncertainties because they are based upon: the amount and timing of future changes in interest rates, market behavior, and other economic conditions; future laws, regulations, and accounting principles; changes in regulatory standards and examination policies, and a variety of other matters. These other matters include, among other things, the direct and indirect effects of economic conditions on interest rates, credit quality, loan demand, liquidity, and monetary and supervisory policies of banking regulators. Because of these uncertainties, the actual future results may be materially different from the results indicated by these forward-looking statements. In addition, Southwest’s past growth and performance do not necessarily indicate our future results. For other factors, risks, and uncertainties that could cause actual results to differ materially from estimates and projections contained in forward-looking statements, please read the “Risk Factors” contained in Southwest’s reports to the Securities and Exchange Commission.

The cautionary statements in this release also identify important factors and possible events that involve risk and uncertainties that could cause our actual results to differ materially from those contained in the forward-looking statements. These forward-looking statements speak only as of the date on which the statements were made. We do

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Southwest Bancorp Inc. Reports Net Income of $5.2 Million for the First Quarter of 2012

not intend, and undertake no obligation, to update or revise any forward-looking statements contained in this release, whether as a result of differences in actual results, changes in assumptions, or changes in other factors affecting such statements, except as required by law.

Southwest is required under generally accepted accounting principles to evaluate subsequent events and their impact, if any, on its financial statements as of March 31, 2012 through the date its financial statements are filed with the Securities and Exchange Commission. The March 31, 2012 financial statements included in this release will be adjusted if necessary to properly reflect the impact of subsequent events on estimates used to prepare those statements.

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Southwest Bancorp Inc. Reports Net Income of $5.2 Million for the First Quarter of 2012

Financial Tables

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Balance sheet amounts and ratios are as of period end unless otherwise noted.

Please see accompanying tables for additional financial information.

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