Okla. Stat. tit. 74, § 250.4a

Any member of the Legislature who may, during the time for which he was elected Senator or member of the House of Representatives, be appointed or elected to any office incident to which the salary or emoluments thereof are increased, shall receive during the term for which he was elected or appointed to such office the salary or emoluments which under the provisions of law appertain to such office at the beginning of the time for which he was elected Senator or member of the House of Representatives.