A mistake by goalkeeper Sam Slocombe gifted them a 17th-minute lead when he flapped at a left-wing cross from Dean Lewington, turning it straight into the path of Luke Chadwick who volleyed home from an acute angle.
It was a first goal in four games for the Dons and they struck again on the half-hour mark. It was Chadwick again with an excellent finish, curling a shot from the edge of the box into the far-top corner of the net.
Without leading marksman Leon Clarke, Scunthorpe played with just one man up front and struggled as an attacking force. Mark Duffy and Josh Walker did force decent saves from keeper David Martin, but the home side never looked like getting back into the game as they slumped badly to their fifth defeat of the season in front of their own fans.
More calamitous defending saw them go 3-0 down on the hour when they failed to deal with a corner knocked high into the box, allowing Alan Smith to pounce with a close range header.
Chadwick should have completed his hat-trick in the 84th minute from the penalty spot but he saw his kick saved by Slocombe after on-loan striker Angelo Balanta had been tripped in the box by Mirfin.