[3] On August 1, 2009, the Reds traded Stewart, along with Edwin Encarnación and Josh Roenicke, to the Toronto Blue Jays for Scott Rolen.

[5] On June 14, 2011, Stewart was called up from the Double-A New Hampshire Fisher Cats to replace Kyle Drabek, who was optioned to the Triple-A Las Vegas 51s.

He made his career debut on June 16, 2011, against the Baltimore Orioles, pitching 7 innings, giving up 7 hits, 2 earned runs, 1 walk and 4 strikeouts.

[7] On July 27, 2011, Stewart was traded to the Chicago White Sox with Jason Frasor for Edwin Jackson and Mark Teahen.

On September 5, 2011, Stewart threw 7 perfect innings before giving up a hit to Minnesota Twins infielder Danny Valencia.

On June 24, 2012, Stewart was traded to the Boston Red Sox with Brent Lillibridge for Kevin Youkilis and cash.

[13] On November 28, 2012, the Pittsburgh Pirates announced that they had acquired Stewart from the Red Sox in exchange for a player to be named later.

[27] On January 26, 2023, the Glacier Range Riders of the Pioneer League hired Stewart to serve as their pitching coach.