Milone (6-5) recorded his third victory in four starts, holding the Brewers to five hits without issuing a walk. The left-hander struck out four as the streaking A's racked up their 10th win in 11 games.
Brandon Moss also went deep for Oakland, which took the opener of a three-game series and moved to within 1 1/2 games of American League West-leading Texas.
Brewers starter Marco Estrada (4-4) was tagged for five runs on nine hits over four full innings.
Rickie Weeks socked a pair of solo homers for Milwaukee.
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