Coulombe was optioned to Triple-A Nashville on Tuesday.
Coulombe didn't impress since his recall on June 4, giving up homers in three of his seven appearances while posting a 4.50 ERA and 1.38 WHIP. He'll head back to Triple-A Nashville now where he's given up only one earned run over 20 innings. In a corresponding roster move, the A's called up speedy second baseman, Arismendy Alcantara.