The Dons, who exited the Co-operative Insurance Cup at the hands of Second Division East Fife on penalties, ensured there would be no cup shock this time around when Scott Vernon opened the scoring after 31 minutes.
Mohamed Chalali added a second 10 minutes later, Rory Fallon headed home on 71 minutes and Mitch Megginson completed the scoring late on to give the Scottish Premier League side a comfortable win against Dick Campbell's men.
With skipper Richard Foster having left Pittodrie to sign for Bristol City and Andrew Considine and Youl Mawene absent through suspension and injury respectively, there was a first start for loan signing Mark Reynolds who joined the Dons from Sheffield Wednesday yesterday.
Kari Arnason was handed the captain's armband in Foster's absence, while there were also starts for Chalali, Clark Robertson and Rory McArdle.
The Dons began to exert their authority early on with Forfar goalkeeper Greg Paterson called upon to keep out a low Ryan Jack drive and a Vernon snapshot in the opening minutes.
The visitors were forced to make an early change when Peter Pawlett limped off and was replaced by Chris Clark with 14 minutes gone.
They had the ball in the back of the net a couple of minutes later when Paterson fumbled a McArdle header over the line, but the goal was chalked off for offside.
And things went from bad to worse for the Dons after only 18 minutes when Isaac Osbourne hobbled off and Fallon was introduced in his place.
The part-timers gave their top-flight rivals a scare when Greg Ross fired just wide at the near post after some strong running by on-loan Dundee United winger Dale Hilson.
But they were to rue that missed opportunity when Aberdeen took the lead after 31 minutes when the home defence failed to deal with Arnason's long throw and Vernon volleyed home.
And the Dons doubled their advantage four minutes before the break when Chalali seized upon an error by Forfar skipper Marc McCulloch and kept his composure to slot the ball past Paterson.
Fallon passed up a golden opportunity to score a third within three minutes of the restart when he failed to direct his header from a Fraser Fyvie corner on target with an open goal at his mercy.
The New Zealand international almost redeemed himself after 62 minutes when he played a neat pass to release Chalali, but Paterson was equal to the Algerian's effort before Chris Templeman went close at the other end with a close-range volley which was well stopped by Jason Brown.
But Fallon eventually got his goal after 71 minutes with a diving header after Chalali had flicked on Vernon's cross to put the result beyond doubt.
And substitute Megginson, who had replaced the tiring Chalali, latched onto a Jack header and rounded the goalkeeper to add a fourth in the closing stages.