The Pirates reinstated Peters (back) from the 15-day injured list Tuesday.
Reliever Eric Stout was optioned to Triple-A Indianapolis to clear room on the active roster for Peters, who had been on the injured list since June 7 with a back muscle spasm. Peters built up to 2.1 innings over his four rehab appearances between Indianapolis and Double-A Altoona, so he should be available as a potential bulk-relief option behind opener Chris Stratton while the Pirates treat Tuesday's game in Miami as a bullpen day.