 Gillis spent his junior hockey career with the Kingston Canadians of the Ontario Major Junior Hockey League (OMJHL) from 1975 to 1978, playing in 111 games and scoring 132 points (39 goals and 93 assists).He added on 18 points (four goals and 14 assists) in 12 playoff games.Gillis missed most of the 1976–77 season due to a leg injury.