Three area men were among nine persons elected last week to the board of the $225 million national Consumer Cooperative Bank as the bank was converted from a government institution to one of mixed ownership.

The Co-op Bank is now controlled by a 15-member board, 12 of whom are elected directly by the cooperatives to which the bank lends.

The new board includes Paul O. Mohn of Silver Spring, chairman of the board of Greenbelt Cooperative and an economist at the Agriculture Department; Morgan Williams of Burke, president of the Washington-based Cooperative League of the U.S.A.; and C. Peter Behringer of Baltimore, owner of Multi-Family Housing Services, Inc., a developer of low and moderate income housing cooperatives in the region.

President Reagan tried unsuccessfully last year to persuade Congress to close the bank, which was created in 1978, on the grounds that creditworthy cooperatives had access to normal sources of credit. In a compromise, stockholder control of the bank was advanced by 30 years and an agreement signed under which the bank will repay the government its capital investment in the bank by the year 2020. After 1990, the bank will pay interest at market rates on the unrepaid investment.

The bank, which began operations in 1980 and has more than $100 million in loans outstanding, made a profit of $4.3 million in the fiscal year ended last Sept. 30.

Three members of the board will still be presidential appointees, though only one, the chairman, Frank Sollars of Washington Courthouse, Ohio, has been named.