Grimsby Town 1 Milton Keynes Dons 3
The visitors scored all the goals in the second half, while Grimsby's only reply was a well struck volley by midfielder Ricky Ravenhill with the last kick of the match.
There was little sign of the second half rout in a generally scrappy first half in which Grimsby more than matched their high-flying opponents.
But the Dons came out for the second period with an extra spring in their step and won the game with two goals inside eight minutes.
Poor marking from a 52nd corner enabled top scorer Izale McLeod to head home easily and then eight minutes later strike partner Aaron Wilbraham lobbed keeper Phil Barnes as the keeper came off his line in a full on bid to stop the danger.
Another corner 12 minutes from time completed Grimsby's misery when Wilbraham scrambled the ball home from close range.
With Grimsby's recent results having been poor the game attracted the smallest crowd this season at Blundell Park.
And an injury to midfielder Kevin James on loan from Nottingham Forrest, who was making his debut, did little to help Grimsby's rhythm. James a fast and skilful player appeared to fall awkwardly and, after a four minute delay, was carried off in a stretcher with a dislocated shoulder injury.
This brought on sub Nick Heggarty and, in added time at the end of the first half, the sub headed wide and then created a good opening for Peter Bore who finished similarly.
But it was a completely different story in the second period as Martin Allen's side carried far too much pace and style for Grimsby who had their second successive defeat.