The Rangers lost eight of 10 following the All-Star break, but this was their fifth straight win and they moved to within 2 1/2 games of the American League West-leading Athletics.
Texas scored a pair of runs in the second, third and fourth innings to overcome an early 2-0 deficit and Oakland managed just three hits against five relief pitchers.
Pierzynski added a two-run single in the seventh, giving him six RBI in his last two games.
Texas starter Alex Ogando lasted just four innings and the win went to Jason Frasor (2-2), the Rangers' third pitcher who worked 1 1/3 perfect innings. Tommy Milone (9-9) was roughed up for six runs on nine hits in 3 2/3 to take the loss.
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