The Bears announced Tuesday they were bringing back Britton after releasing him at the end of the preseason. He appeared in the final 13 games for Chicago last season.
Garza and Slauson were injured in the season-opening loss to Buffalo. The Bears visit San Francisco this week.
Chicago also released receiver and kick returner Micheal Spurlock on Tuesday. He had one catch for 8 yards and saw time as a punt returner with a fair catch against Buffalo.