Okla. Admin. Code § 45:30-5-19
When attending a trade show or festival, the location within the trade show or festival occupied by the brewery becomes a licensed premises and extension of the licensed brewery. The licensee shall set up and define an area contiguous to their booth space as a serving area where the beer is dispensed. Therefore, a 21 years of age and older serving area shall be established and a Type II sign stating " No Persons under 21 Years of Age Permitted In This Area of These Premises" shall be posted at the entrance to the serving area or bar top. The licensee may only serve the beer in the serving area. In the event that multiple brewers are at the same festival, they may combine their 21 year old and older serving areas into one larger area as long as they are contiguous to the brewer's booths.
Okla. Admin. Code § 45:30-5-19