Pitcher Clayton Richard was sent in as a pinch-hitter with two outs in the 13th and collected a single off David Pauley (0-1). The next batter, Venable, worked the count to 3-2 before lining a hit to left field that was bobbled by the Angels' Howie Kendrick.
Richard chugged around third and scored standing up when the throw was late, and San Diego took the rubber match of its three-game set against the Angles.
The rally handed the victory to Miles Mikolas (1-1), who tossed two scoreless frames for the Padres.
Yonder Alonso went 2-for-4 with two RBI for San Diego.
Mike Trout had three hits, including a solo homer, for Los Angeles.
The two teams left a combined 26 men on base.