Okla. Stat. tit. 36 § 4112
An insurer shall pay the proceeds of any benefits under group life insurance policy not more than thirty (30) days after the insurer has received proof of death of the insured. If the proceeds are not paid within this period, the insurer shall pay interest on the proceeds, at a rate which is not less than the current rate of interest on death proceeds on deposit with the insurer, from the date of death of the insured to the date when the proceeds are paid. Payment shall be deemed to have been made on the date an electronic payment is made or a check, draft or other valid instrument which is equivalent to payment was placed in the U.S. mails in a properly addressed, postpaid envelope; or, if not so posted, on the date of delivery of such instrument to the beneficiary.
Okla. Stat. tit. 36, § 4112