The 32-year-old forward could play alongside Usain Bolt for the Mariners, as the eight-time Olympic gold medallist is on trial with the club.
McCormack spent last season on loan with fellow Australian side Melbourne City, and has also played for Cardiff City, Leeds United, Fulham and Nottingham Forest in recent years.
The Scottish international struggled to make an impact at Villa Park, scoring just three goals in 24 appearances and having not featured since September 2017.
Central Coast Mariners finished bottom of the A-League last season and will hope to improve this campaign.