Steve Pearce socked a three-run homer in the first inning, which turned out to be all the O's needed as Ubaldo Jimenez and four relievers held the Blue Jays to four hits and a pair of runs in an 8-2 rout.
The win was Baltimore's third straight and ninth in their last 10, as they streak toward their second playoff appearance in the last three years. They've taken the first two from Toronto at Camden Yards and will play the final game of the series on Wednesday, beginning at 7:05 pm EDT at Camden Yards.
The O's finish their regular season at the Rogers Center in Toronto with three games against the Blue Jays, but, prior to that, they will get to take victory laps against the Red Sox in Baltimore (three games), followed by a four-game series in New York with the Yankees.
Baltimore has a chance to finish with the best record in the league, though they trail the Angels in that department by three games. LA can clinch the West with a win over Seattle, Wednesday night.
Ian Desmond doubled and homered, drove in two runs and scored twice while Tanner Roark blanked the Braves over seven innings in the pennant-clincher.
Roark (14-10) allowed five hits, did not issue any walks and struck out four. Tyler Clippard and Drew Storen finished up with perfect eighth and ninth innings, respectively. Storen picked up his seventh save.
The first NL team to claim a playoff spot, the Nationals currently have the best record in the league, which would assure them of home field throughout their playoff run. They lead the Dodgers - currently on top in the NL West by three games over the Giants - by 1 1/2 game.
With eight wins in their last ten games and winners of four straight, the Nationals finish up with the Braves for the year in game three of their series in Atlanta, Wednesday night at 7:00 pm EDT.
A quirky schedule has the Nationals playing Miami eight times in the final two weeks, starting with four games in Miami this week, and four to close out the season in Washington. Sandwiched in between is a three-game series with the Mets at home.