Butler went 3-for-4 and Eric Hosmer added three hits and two RBI with two runs scored as the Royals won for the third time in five games.
Greg Holland (4-1) tossed a scoreless eighth to secure the victory for the Royals, who got two RBI each from Jeff Francoeur and Mike Moustakas.
A's closer Andrew Bailey (0-4) coughed up three runs on three hits in the final inning to suffer the loss.
Oakland's Scott Sizemore pounded a three-run homer.
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