Villa paid Fulham £12m for the Scotsman's signature in 2016.
He went on to make 24 appearances in four seasons, which included loan spells at four different clubs.
McCormack still had 12 months remaining on his contract and was in line for a pay increase after Villa's promotion to the Premier League.
However, the two parties have reached a mutual agreement to terminate the contract.
"The club would like to wish Ross well for the future."