Stewart was recalled from Triple-A Buffalo on Thursday, Mike Wilner of Sportsnet 590 The Fan reports.
Stewart has made three appearances for the Blue Jays since being claimed off waivers at the end of July, posting a 3.77 ERA, 1.19 WHIP and 10:3 K:BB across 14.1 innings in those outings. He'll likely fill a long-relief role for the stretch run, while he could also make an appearance or two as a primary pitcher.