Okla. Admin. Code § 45:35-1-6
If the event will include patrons of all ages, the alcoholic beverages shall only be distributed from a designated bar area in which only person(s) 21 years old or older may enter. There shall also be a Type II sign posted at the entrance to the designated bar area. The sign shall state "No Persons under 21 Years of Age Permitted in This Area of These Premises." If the event will have only patrons that are 21 years of age or older, a Type I sign that states "No Persons under 21 Years of Age Permitted on These Premises" shall be posted at the event entrance. In order for to qualify for a Type II designation, the applicant must derive more than 51% of their income from something other than the sales of alcoholic beverages.
Okla. Admin. Code § 45:35-1-6