Goals from Richard Cresswell and Michael Doyle gave Danny Wilson's men a two-goal lead at half-time with Lee Williamson scoring twice in the second half.
Cresswell (18) opened the scoring with a firm downward header after getting on the end of a cross from Stephen Quinn. Keeper Steve Simonsen then protected United's lead with a good save down to his right from Andrew Williams.
Doyle had a header saved before he found the net in the 37th minute with a well-struck effort from 25 yards and Williamson (47) scored with a shot from just inside the area to make it 3-0.
Yeovil rarely posed an attacking threat with Williams shooting wide and Paul Huntington putting a header just over.
Matt Lowton headed wide before Williamson (87) rounded off the scoring with a shot from an acute angle which deflected off keeper Rene Gilmartin's leg.