Aylesbury were made to pay for a lack of conviction in the final third of the pitch, as they racked up their 16th match without a win.
Neil Trebble selected a positive looking team, with three strikers on the pitch, and handed a full debut to keeper Reece Kirk, as well as a starting spot for new loan signing Gary Schillachi.
The opening stages were excellent from Aylesbury, as they looked to put their hosts under some early pressure. A goalbound header was cleared off the line in just the second minute.
Then came what proved a decisive moment in the game. Using his pace to good effect Roni Joe burst into the area, but was felled by goalkeeper Mario Ziccardi. The referee, to much anger from the home crowd, awarded a penalty. Unfortunately Leon Gutzmore's attempted chip looped over the bar.
It would have been a critical point to score, but instead Grantham grew in stature and started playing some neat football. Adam Sturgess headed a corner over when he might have done better, before Kirk was forced to palm away another dangerous inswinging set piece minutes later.
After thirteen minutes disaster struck for United. Jason Turner picked up the ball 30-yards from goal, looked up to see Kirk well off his line, and sublimely lobbed the ball over his head and into the net. 1-0 Grantham
This triggered the home side's best spell of the game, as Aylesbury could barely get near the ball, let alone string two passes together. When United did have possession, an apparent lack of creativity in midfield was a recurring problem.
Turner threatened again, spinning free of the offside trap, but his end product was only a powder-puff shot straight at Kirk.
He was at it again just three minutes later, and this time made the effort count. Kirk may feel he could have done better, after showing little conviction when coming out to meet the Grantham forward, who easily slotted the ball home. 2-0 Grantham
Richard Challinor saw an effort deflected wide on the edge of the box, as the half drew to a close, and forced another corner which caused more mayhem in United's area.
Aylesbury fashioned a chance just before the break, when a free-kick was quickly taken to Paul Kelly in the right channel. His cross was headed just over by Matt Hayward.
Half-time: Grantham 2-0 Aylesbury
It was going to require something special from the Ducks to turn around a two-goal deficit, but they began the second period brightly. Richard Pringle did well down the left and cut the ball back for Kelly to the ball goalwards, but Ziccardi was up to his first real test of the afternoon and palmed clear.
Schillachi was often a menace down the right, and one probing run produced a superb flighted cross, which Leon Gutzmore at the far post should have buried, instead of heading over the bar.
As United pushed forward, they left themselves exposed at the back, but Grantham wasted the few chances they created. Richard Sturgess found himself with a clean sight of goal, but fired well over, and Challinor blazed over from the opposite side after Bacon had hit a hanging cross-shot.
With the minutes ticking away Aylesbury's frustration was growing, and they could only produce meaningless long-range shots to try and test Ziccardi. Pringle and Kelly both hit 25-yarders which were never going to hit the target.
In the final ten minutes two substitutes went close for the Ducks, firstly Aston Goss who turned sharply in the area but shot just wide. Then Damon Ming cut inside, but fired his effort straight into Ziccardi's arms.
Once again, there are positives to be taken in defeat, but its points that Neil Trebble's team need, and quickly...
