O'Neill was born in Malone, New York and attended McGill University in Montreal, Quebec, Canada. He lettered in basketball for three years in college, 1976–79, and in 1978 the McGill Redman had a school-record 28 win season and entered the Canadian Interuniversity Sport men's basketball championship tournament. He graduated from McGill in 1979 with a bachelor's degree in education, and later earned his master's degree in secondary education from Marycrest College in 1983, where he also served as head coach of the NAIA basketball team for the 1982–83 season.