The home side made the kind of start managers must dream of when they opened the scoring after only four minutes from an unlikely source.
Grant Brebner gave away a bizarre free-kick out by the corner flag and Kevin McBride's delivery was powerfully headed high into the top left hand corner of the net by David Partridge, for his first goal of the season.
Motherwell looked to capitalise on this start and Jim Hamilton saw his shot slip wide from 25 yards.
United were forced to replace David McCracken after 11 minutes when he fell awkwardly after a challenge on Hamilton.
This seemed to galvanise the visitors who have levelled if it were not for Gordon Marshall reacting well to save from Jason Scotland and Stephen Craigan clearing off the line as James Grady tried to force the ball over the line.
The remainder of the half was poor fare until the dying stages when Well striker Scott McDonald turned Alan Archibald at the edge of the box but his effort was well saved by Tony Bullock.
At the other end Stevie Crawford managed to scuff a shot wide with no one near him and then as the half came to a close Grady saw a half-hit shot rebound off the junction of crossbar and post.
Well made a quick start to the second half within two minutes Archibald slipped as he went to clear the ball from an innocuous pass, allowing McDonald to run free on goal and coolly slot the ball past Bullock for his 11th goal of the season.
Once again they tried to push home their advantage but found Bullock in the visiting goal in fine form as he dived full length to beat out a Jamie Paterson right footer.
Bullock was helpless minutes later but McDonald's header flashed just past his near post.
He was called upon again to deny Partridge his second goal, and needed help from Grady to prevent Paterson scoring from the rebound. Bullock also held a flashing McDonald header just under his bar after 63 minutes.
United then made their best chance of the half when a cross from the right found Barry Robson in acres of space six yards out, but he somehow managed to pull his shot wide of the far post from close range.
Motherwell held out comfortably to go four games unbeaten and make it three clean sheets in a row in the process.