Jon Turcott finished alone in second place at 11-under-par 202 after a round of 68. Peter Tomasulo was two shots off the pace at 10-under-par 203. Overnight leader Matt Hansen struggled with a 74 on Saturday to fall back into a tie for fourth place with Bobby Kalinowski at 9-under-par 204.
McQuillan collected a pair of birdies over his first three holes at Edmonton Country Club. He found trouble with a bogey at the fourth but recovered with back-to-back birdies from the fifth.
The Canadian birdied the eighth and added a birdie at the par-4 17th to hold the outright lead.
'I had some breaks early on, but I played very well, especially on a day like today,' said McQuillan. 'I have some good memories of this place from last year. I'll go out tomorrow, give it my best and see where I am.'
Lee Williamson, Brian Guetz, Luke Hickmott, Todd Tanner, Paul Danielson and Brian Payne are knotted at 8-under-par 205.