Hunter (2-1) held the Blue Jays to one run on three hits, walking three and striking out three as the Orioles won for the seventh time in 11 games.
Three relievers combined for two scoreless innings and Pedro Strop collected his first major league save for the Orioles, who took the opener of a three-game series at Camden Yards.
Wieters broke a 1-1 tie in the fourth inning when he sliced a pitch toward the left-field wall. Toronto's Eric Thames leaped for the ball but it bounced off his glove and over the fence for a solo home run.
Thames blasted a long homer himself for the Blue Jays.
Henderson Alvarez (0-2) absorbed the loss, surrendering two runs on five hits in a seven-inning start.