Lopez delivered a three-run triple in the eighth inning that snapped a tie game.
On Monday, the Orioles purchased the contract of Tim Raines Jr. from Class AAA Rochester and prior to Wednesday's game, they acquired his father from the Montreal Expos.
The only other father-son duo to play in the majors was that of Ken Griffey Jr. and Ken Griffey Sr., who played with Seattle in 1990-91.
Raines Jr. started the game in center field and was two for four with a walk and his father entered the game as a pinch hitter for Chris Richard in the seventh.
As for the game, Orioles reliever Buddy Groom (1-4) came into the contest in the eighth with the score tied, 4-4. He allowed three straight singles before giving way to Jorge Julio, who grooved an 0-1 pitch that Lopez laced into right-center field to clear the bases.
Toronto's Pasqual Coco struggled through his first major league start. Coco, who made six relief appearances this season, allowed three runs and five hits in 4 1/3 innings.
Coco left with the game tied, 2-2, and Kevin Beirne gave up a doubles to Luis Matos and Jeff Conine in the fifth. Beirne allowed two runs and three hits in two innings before Scott Eyre (1-2) retired a pair of batters.
Bob File tossed a perfect eighth and closer Billy Koch worked around two runners in the ninth to record his 36th save in 43 chances.
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