Steve Pearce delivered a two-run double off Red Sox reliever Franklin Morales with one out in the bottom of the eighth to give the Orioles a 6-5 lead.
Pearce has doubled twice and driven in a season-high three runs tonight. It's his third multi-RBI game of the season and his first three-RBI game since Aug. 11, 2012.
Matt Wieters and Danny Valencia singled to start the rally. Nick Markakis struck out after almost hitting an opposite-field three-run homer, and Pearce moved the Orioles ahead.
Pinch-runner Nate McLouth scored the tying run and Valencia slid home safely with the go-ahead run on another aggressive send by third base coach Bobby Dickerson.
Dickerson has been an outstanding replacement for DeMarlo Hale. He also draws high praise for his work with the infielders.
Jonathan Schoop was announced as a pinch-hitter for Jason Pridie, but Ryan Flaherty batted after right-hander Brandon Workman replaced Morales.
Schoop didn't start tonight because of soreness that the Orioles feared may have been linked to the stress fracture in his back earlier this summer. He wasn't expected to be available.
Jim Johnson will pitch the ninth, going for his 49th save.
Kevin Gausman stands to be the winner if Johnson holds the lead. He struck out two in 1 1/3 perfect innings.
The Orioles are 18-31 in one-run games. They're 71-9 when leading after eight innings.
Update: Game over. Johnson stranded the tying run at second base for his 49th save, and the Orioles defeated Boston 6-5.
Johnson got a called third strike on Jonny Gomes to end the game and improve the Orioles' record to 84-77.
The Orioles have won consecutive season series against the Red Sox for the first time since 1991-92.