Manager John Gibbons announced the news before Wednesday's game against the New York Yankees.
Hutchison will pitch in the Blue Jays' second regular-season game Tuesday at Tampa Bay. McGowan beat out several other fifth-starter contenders and is lined up to pitch the home opener with the Yankees on April 4.
McGowan has pitched in just 30 big league games, including 25 relief appearances last season, since right shoulder surgery in July 2008.
"He was one of the top up-and-coming pitchers here in this organization a few years ago," Gibbons said. "It's pretty amazing in my mind that he's come back this far. We're going to run with it and see where it takes us."
Left-hander J.A. Happ, who was in the mix for the final rotation spot, will start the season on the disabled list with back tightness.