Bray strained his groin during spring training, putting him behind in preparation for the season. He aggravated the injury during an 11-1 loss to St. Louis on April 18, when he gave up three hits and three runs. The Reds put him on the 15-day disabled list.
Last season, Bray was second in the NL with 79 appearances. He's made only five this season.
Bray began a rehab assignment on June 9 and had no problems.
"It's been a long couple of months. It's nice to be back," Bray said. "Everything feels good."
Right-handed reliever J.J. Hoover was optioned to Triple-A Louisville to open a roster spot. Hoover was called up when Bray went on the DL and was 1-0 with a 3.00 ERA in 17 appearances.
Hoover's performance impressed the Reds, who had planned to keep him around a few weeks longer.
"It was a very tough decision," manager Dusty Baker said. "J.J made it a tough decision. Bray was ready a lot quicker than we anticipated. We thought it might be midseason. We hope J.J's going to be here a long time. It's a numbers thing. He'll be back."
The plan during spring training was to use Bray, Marshall and right-hander Nick Masset in the setup role for closer Ryan Madson. Bray hurt his groin, Masset developed a sore shoulder and Madson tore a ligament in his pitching elbow, forcing Baker to move Chapman from a starting role to the bullpen.
Also Friday, the Reds sent center fielder Drew Stubbs to Class-A Dayton for a weekend rehabilitation stint. Stubbs pulled muscles in his side on a swing on June 14. He can be activated at any time.
The Reds want him to play a few games in the minors to see how his side reacts.
"A lot depends on how he feels," Baker said. "You hope there's no setbacks. We're hoping it's just three days."