Okla. Admin. Code § 590:10-7-1
For those members with a retirement date prior to July 1, 1998, to achieve equity among all members in computing the final average compensation, the highest thirty-six months of salary, excluding longevity payments, earned during the last one hundred twenty months of participation separately for service prior to July 1, 1994 and for service after July 1, 1994, subject to the maximum compensation level, will be averaged. Exceptions are yearly contract employees at the School for the Blind and the School for the Deaf for whom the two highest annual salaries will be used and the third year (twelve months) will be composed of the next twelve highest average monthly salaries. To compute the final average compensation for Post July 1994, (1) annualize using the full months of salary only, and (2) add the pro-rated longevity to the product of #1 before dividing. This Post July final average compensation procedure will apply to all such members vesting or retiring with less than three (3) years of salary after July 1, 1994. Those members paid bi-weekly will have twenty-six pay periods included in each annual (twelve months) salary total.
Okla. Admin. Code § 590:10-7-1