Sartain was born in Tulsa, Oklahoma, the son of a Tulsa fire chief. He attended Cascia Hall Preparatory School, is a 1963 graduate of Will Rogers High School in Tulsa and was a member of the Epsilon Mu chapter of the Kappa Sigma Fraternity at the University of Tulsa, from which he graduated with a Bachelor of Fine Arts degree. In 1968, Gailard moved to New York City, where he worked as an assistant to Illustrator Paul Davis.
Discovered by a talent scout during his stint as Mazeppa, Sartain was hired in 1972 as a regular on the television program Hee Haw. Sartain remained as a regular cast member of the popular show for nearly 20 seasons. He also served as a regular on other series including Cher (1975–76) and Shields and Yarnell (1978). Sartain played C.D. Parker for one episode during the pilot season of Walker, Texas Ranger. He supplied the voice of a social worker in the pilot episode of the animated series King of the Hill. Sartain also portrayed an advisor to Louisiana Governor Earl Long (played by Paul Newman) in the movie Blaze.
Sartain has appeared in more than forty motion pictures, most notably as The Big Bopper in The Buddy Holly Story, Sheriff Ray Stuckey in Mississippi Burning, The Outsiders, The Hollywood Knights, Fried Green Tomatoes, The Replacements as Offensive Assistant Coach Leo Pilachowski,The Big Easy, The Grifters, Getting Even with Dad, The Patriot, and an uncredited role in the 1994 comedy Wagons East starring John Candy and Richard Lewis.
His most recent film role was in 2005, in Cameron Crowe's Elizabethtown. He is also known for his role as Chuck in three of the Ernest P. Worrell films starring Jim Varney (as well as the Hey Vern, It's Ernest! television series). With fellow Hey Vern co-star Bill Byrge of Nashville, the duo performed as brothers Chuck and Bobby in a series of "Me and my brother, Bobby..." pitches for local TV stations and product ads.
