The Blue Bombers also acquired a fifth-round pick while sending a third-rounder to the Argos, TSN's Farhan Lalji reports. The third-rounder becomes a first-rounder if Collaros re-signs with Winnipeg.
Collaros, 31, began the season with the Saskatchewan Roughriders before being traded to the Argos on July 31.
The veteran didn't appear in a game for Toronto after suffering a concussion in Week 1 against the Hamilton Tiger-Cats.
Blue Bombers pivot Matt Nichols remains sidelined with an upper-body injury suffered in August, and Collaros provides the club with a reliable replacement.
Collaros threw for 2,999 yards, nine touchdowns, and 13 interceptions over 14 games with the Roughriders in 2018.
Winnipeg (9-6) sits third in the West Division, but the team has lost three consecutive contests and will look to break that slump in Week 18 against the Montreal Alouettes.