Okla. Stat. tit. 19 § 4
In all suits or proceedings by or against a county, the name in which a county shall sue or be sued shall be, "Board of County Commissioners of the County of _____," but this provision shall not prevent county officers, where authorized by law, from suing in their official name for the benefit of the county. Suit may be brought against a county by naming a county officer identified in Section 161 of this title when it is alleged that such officer in his or her official capacity is directly or vicariously liable to plaintiff in an action not arising out of contract. Otherwise, suit may be brought against a county by naming the Board of County Commissioners of the County of _____; in actions against the Board not arising out of contract, upon motion, the Court may substitute a county officer identified in Section 161 of this title in his or her official capacity for the Board upon a showing that such county officer is better suited to represent and defend the county under the particular facts of the case.
Okla. Stat. tit. 19, § 4