The Villans are hoping to get a deal finalised within the next 24 hours.
The forward had been expected to complete a move to Norwich City, who were hoping to push through a deal for the Scotland international.
They had offered £11 million plus an extra £1 million as they looked to sign the striker that their squad has been sorely missing for a number of years.
However, Villa have now allegedly made a late move to secure his signature from under the noses of their Championship rivals.
According to the Daily Mail, Villa chairman Tony Xia has sanctioned a £12 million offer that also includes add-ons based on promotion.
Manager Roberto di Matteo is now hoping to have the deal for McCormack wrapped up within the next 24 hours.
The Italian will be hoping the striker can come in and solve the goal-scoring issues that plagued Villa as they were relegated from the Premier League last season.
McCormack certainly has goal-scoring pedigree in the division with 42 goals in the last two seasons alone, and Villa will be keen to see him replicate that at Villa Park should he join.