McGuire signed a minor-league contract with the Reds on Thursday and was assigned to Triple-A Louisville.
He debuted for Louisville on Saturday, covering 4.1 innings while giving up five earned runs on four hits and two walks. The 32-year-old right-hander previously made 27 big-league appearances with the Reds, Blue Jays and Angels between the 2017 and 2018 seasons, logging a 5.23 ERA and 1.47 WHIP across 51.2 innings. He most recently pitched in the independent Atlantic League of Professional Baseball with the Gastonia Honey Hunters before landing the minor-league deal with Cincinnati.