The move came Tuesday, three days after Ross was designated for assignment.
The A's signed Ross on April 8 following his release by Arizona four days earlier. It was a cost-efficient move for Oakland, which was only responsible for $499,180, a prorated portion of the $507,500 league minimum. Ross was guaranteed $8.5 million this year as part of his contract with the Diamondbacks.
Ross batted .091 with no home runs and three RBIs in nine games with the A's.