McGowan, who officially made his return to the Majors in a relief appearance on Tuesday against the Red Sox, will toe the rubber in the Blue Jays' series finale against the Orioles.
"That's what I wanted to do," said McGowan, on earning a crack in the rotation. "I've got to get ready to do it."
The once highly touted right-hander -- returning from multiple surgeries to his shoulder and knee -- expected to finish the season in Toronto's bullpen, despite hearing speculation might get the chance to start.
"I was a little bit shocked," McGowan said. "I honestly didn't even think about it. I didn't even know if I'd be starting this year at all. So yeah, it was a complete surprise."
McGowan threw four innings on Tuesday, surrendering three runs on five hits. He consistently hit the mid 90s on the radar gun.