He is married with one daughter and two sons and resides in California.
O'Bannon grew up the son of a gaffer, surrounded by film from his birth. His father worked on various films through Warner Bros. golden age, and his mother was a professional dancer who performed with Fred Astaire.
He started writing in high school, and wrote many spec scripts, and eventually submitted them to NBC's Amazing Stories and CBS's The Twilight Zone (1985). CBS bought one of them, and after a second script sale for The Twilight Zone, he was hired on as a staff writer.