Neil Wagner (1-1) came in to pitch with two outs and the score tied 4-4 in the seventh, when Beltre greeted him by belting a pitch the opposite way over the right-field wall for a solo home run, his 14th homer of the season.
David Murphy added an insurance run with a bases-empty clout in the next frame and the Rangers hung on to take the rubber match of a three-game series.
Nelson Cruz homered and contributed two RBI for Texas.
Neal Cotts (2-0) earned the victory with one inning of shutout relief and Joe Nathan racked up his 19th save for Texas, which came into the contest one-half game behind first-place Oakland in the American League West.
Adam Lind cracked a three-run homer for the Blue Jays.
Toronto's Jose Bautista went 3-for-4 before being thrown out of the game in the ninth inning for arguing a strike call with home plate umpire Gary Darling.