Okla. Stat. tit. 12, § 729.10

A. With respect to a foreign-money claim, recovery of prejudgment or pre-award interest and the rate of interest to be applied in the action or distribution proceeding, except as provided in subsection B of this section, are matters of the substantive law governing the right to recovery under the conflict-of-laws rules of this state. B. The court or arbitrator shall increase or decrease the amount of prejudgment or pre-award interest otherwise payable in a judgment or award in foreign money to the extent required by the law of this state governing a failure to make or accept an offer of settlement or offer of judgment, or conduct by a party or its attorney causing undue delay or expense. C. A judgment or award on a foreign-money claim bears interest at the rate applicable to judgments of this state.