"[Cook] just wasn't throwing the ball over the plate. When he did, they hit it," A's manager Bob Melvin said. "He's got to iron that out."
Josh Phegley homered, doubled and drove in three runs to lead the A's, while starting pitcher Kendall Graveman threw 4 2/3 scoreless innings.
Phegley slugged a home run leading off the third inning against Dodgers starter Zack Greinke. In the fourth inning off reliever Chris Hatcher, Phegley doubled over the head of right fielder Scott Van Slyke. That scored Billy Butler, who had walked, and Jason Pridie, who had cashed in Marcus Semien's infield single with an RBI fielder's choice.
Graveman allowed two hits and Oakland's defense turned a pair of double plays on Juan Uribe grounders.
Darwin Barney had three hits for the Dodgers, including an RBI double in a two-run sixth inning that included an RBI groundout by Adrian Gonzalez.