Chris Davis hit a two-run triple for Texas, which has won two of its last three games and remained seven games behind the Boston Red Sox in the AL Wild-card chase. The Rangers trail the first-place Los Angeles Angels in the AL West by 7 1/2 games.
Kevin Millwood (11-10) went seven innings, allowing one unearned run on three hits for Texas.
Edgar Gonzalez (0-3) went 3 1/3 innings, allowing six runs on nine hits for the A's, who lost for the first time in their last nine games.
Matt Carson had a two-run home run for Oakland.