Okla. Stat. tit. 19, § 866.19

The board, within its area of jurisdiction may provide for the termination of nonconforming uses either by specifying the period or periods within which they shall be required to cease, or by providing a formula or formulas whereby the compulsory termination of nonconforming use shall be so fixed as to allow a reasonable period for the recovery of amortization of the investment in the nonconformance, provided, that in each instance any such action of the board shall be taken only after public notice and hearing thereon has been had before the commission and that commission's recommendations with respect thereto certified to the board.