McQuillan turned professional, and finished 7th at the 2003 Spring qualifying tournament for the Canadian Tour. His most successful Canadian Tour result to date has been a victory at the 2005 Telus Edmonton Open, scoring 13-under-par 271 at the Edmonton Golf & Country Club, from 30 June to 3 July; McQuillan edged the runner-up, promising amateur Graham DeLaet, and won $24,000 (Canadian funds). McQuillan played in three Nationwide Tour events in 2005, with his best finish a tie for 25th position in the Alberta Classic.