Jarrod Parker (7-6) yielded two runs on six hits and two walks through six innings, striking out six for American League West-leading Oakland, which snapped the Rangers' five-game winning streak.
Sean Doolittle and Ryan Cook each pitched a scoreless inning of relief and Grant Balfour notched his 29th save as the A's upped their divisional lead over second-place Texas to 3 1/2 games.
Matt Garza (1-1) took the complete-game loss, yielding four runs on eight hits over eight innings. He walked one and fanned five.
McPhee, Cokas 'working on their marriage' after affair
Beautician charged with giving client fatal silicone butt injection