McGowan, who will turn 33 before the start of the 2015 season, appeared in 53 games, making eight starts, for the Toronto Blue Jays in 2014. The 6-foot-3, 240-pound pitcher amassed a 4.17 ERA over 82 innings, earning a 5-3 record.
In seven seasons in Toronto in 2005-2008, 2011 and 2013-2014, McGowan compiled a 4.57 ERA with 392 strikeouts in 482.1 innings. He had a 25-27 record, starting 68 of his 158 games.
The Blue Jays selected McGowan in the first round of the 2000 First-Year Player Draft.
McGowan has long battled injury concerns, and he was last a full-time starting pitcher in the majors during the 2007 and 2008 seasons, when he appeared in a combined 46 games for the Blue Jays.