Charlie Seaman put disjointed Doncaster ahead but Ayoub Assal levelled for Wimbledon before McCormick netted the winner 16 minutes from time.
The visitors had the better of the opening half with Rovers, complete with 10 debutants, struggling for cohesion.
However, Doncaster roared into life in the second half and took the lead 40 seconds in.
After good hold-up play from Tiago Cukur, the ball was lofted into the box with Seaman bringing it down and lashing into the far corner from 15 yards.
Wimbledon pushed hard after falling behind and ensured Rovers’ lead only lasted until the 57th minute.
After the ball ricocheted around on the edge of the box, it was played through low for Assal, who slotted into the bottom corner from 12 yards.
Wimbledon continued to look the stronger side and took the lead in the 74th minute.
After Matt Smith was adjudged to have handled on the edge of the box, former Chelsea youngster McCormick curled a free-kick into the bottom corner for what would prove to be the winning goal.
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