Goals from Clayton Donaldson, Marcello Trotta and Sam Saunders gave the Bees a three goal cushion before Lee Hodson's reply for the visitors.
The win was a 11th success in a current 12-game unbeaten run for the Londoners, who took the lead with just two minutes gone when Donaldson out-muscled Dean Lewington to lash a shot past Dons goalkeeper David Martin.
Trotta doubled the lead shortly after the break when he picked his spot from the edge of the box after an incisive Saunders pass.
And the Bees stretched their advantage further after 58 minutes as the impressive Saunders drilled a superb shot just inside the far post from 20 yards out.
Hodson replied for the Dons in the 73rd minute with a rasping drive that beat David Button at his near post as the visitors looked for an unlikely way back into the game.
Dons dangerman Patrick Bamford screwed a shot wide when clean through before seeing a strong penalty shout waved away by referee Andy D'Urso as the game drifted away from Karl Robinson's side.
Brentford should have been out of sight by the break but a superb Martin save from Alan McCormack and a Trotta volley that flew just over the angle kept it tight.