Seth Smith walked to open the inning and, after Barry Enright (0-1) got two outs, Moss connected with an 0-1 pitch for his second home run of the game and fourth of the season.
That ended the longest game in either team's history at 6 hours, 32 minutes and was the longest Oakland game in number of innings since a game in August 1972 against the Chicago White Sox. It was only the third time the Angels played a game with so many innings.
Jerry Blevins (2-0) -- the eighth Oakland pitcher -- had 1 2/3 innings of one-hit relief and collected the win.
The Angels led 7-2 going into the bottom of the eighth but Oakland rallied for four runs, with a two-run single by Josh Donaldson the big hit, in the inning. The A's tied the score in the ninth when Coco Crisp walked, took second on a fly ball and stole third to get in position for a Yoenis Cespedes RBI single.
Los Angeles took an 8-7 lead in the 15th when J.B. Shuck walked with the bases loaded but an error and a walk set up an RBI single from Adam Rosales in the bottom of the inning to extend the game.