Second-half goals from James Tarkowski and Clayton Donaldson secured the points in a one-sided affair at Griffin Park.
Centre-back Tarkowski broke the deadlock on the hour, rising highest at the far post to head Jake Bidwell's whipped free-kick past Owain Fon Williams.
And the Bees made sure of the points when Donaldson headed Alan Judge's pinpoint cross home from point-blank range after 73 minutes.
But the visitors had their chances before the break, Ryan Lowe's rising drive bouncing to safety off the top of the bar.
And big defender Stephen Arthurworry also hit the woodwork with a header from Jason Koumas' corner on the stroke of half-time.
Lowe also went close when he latched onto a poor Tarkowski header back to the keeper, but stopper David Button was out quickly to quell the danger.
But it was always Brentford who looked more likely to find the net after the break as they took control.
Donaldson twice headed narrowly wide and found the upright with an angled drive while Marcello Trotta tested the side netting with a low drive.