The Jays tweeted that the six-foot-three right-hander will start the home opener April 4 against the New York Yankees.
Knuckleballer R.A. Dickey will open the season March 31 in Tampa, followed by Drew Hutchison, left-hander Mark Buehrle, Brandon Morrow and McGowan.
McGowan beat out the likes of J.A. Happ, Esmil Rogers and Todd Redmond.
Happ, whose back had been troubling him, will start the season on the disabled list.
In another roster move, the Jays sent catcher Erik Kratz to the minors. That means Josh Thole will serve as Dickey's personal catcher.