Nick Markakis crushed a go-ahead solo home run in the top of the 11th as the Orioles downed the Nationals, 2-1, to open a three-game series and begin the seventh annual Beltway Series.
Ryan Mattheus (2-1) came on to pitch the top of the 11th and got J.J. Hardy to fly out before Markakis belted his seventh of the year deep into the right- field seats to give the O's a one-run lead.
"A game like that is frustrating," remarked Washington skipper Davy Johnson. "We pitched good. I thought the bullpen pitched good -- one pitch, ball game."
Kevin Gregg (2-1) got the victory after tossing a scoreless bottom of the 10th and Pedro Strop closed the door in the 11th for his third save of the season.
Adam Jones finished with two hits and knocked in a run as the O's won their fourth straight overall and eighth straight on the road.
"Hopefully it bodes well mentally," Orioles manager Buck Showalter said. "It's a loose clubhouse. There's a lot of confidence in close ball games."
Eight straight road wins is the club's longest such streak since they won 10 straight on the road from August 29-Sepetmeber 24, 1999.
Ian Desmond smacked a game-tying solo shot in the sixth to account for the only run for the Nationals, who have dropped four of their last six.
Xavier Avery coaxed a leadoff walk to start the game and moved to third on Markakis' double two batters later. Jones then smacked a single up the middle that hit Edwin Jackson's foot and shot straight up into the air, allowing Jones to cruise into first with a single while Avery touched home to give Baltimore a 1-0 lead.
Desmond then tied the game in the sixth with one swing of the bat, launching the first pitch he saw into the seats in left field to knot the game at 1-1.
That was it for the offense until the 11th as both starters were able to keep the scoring at a minimum.
Jake Arrieta struck out nine over seven innings for Baltimore and allowed just one run on six hits and a walk while Jackson tossed eight innings of one-run ball for the Nats, scattering five hits and fanning eight.
Baltimore pulled even in the all-times series with Washington at 26-26. The clubs split six meetings a season ago...Tonight's win moved the Orioles to 12 games over .500 for the first time since June 23, 2005 when they were 42-30...Washington went 0-for-5 with runners in scoring position and stranded six.