Gary Alexander and Charlie MacDonald scored the goals as Brentford recorded a second away win in four days.
High-flying Colchester United were beaten at the Weston Homes Community Stadium to give The Bees a fourth successive League One away win.
Brentford started brightly - clearly boosted by Saturday's win against Plymouth Argyle, they had the better of the first half hour.
Marc Tierney had an early deflected shot saved by Richard Lee but most of the goalmouth action was at the other end.
Leon Legge was just unable to reach a far post cross and Ben Williams saved a low Sam Saunders shot.
Alexander had a great chance when a free kick dropped to him eight yards out but Williams saved his powerful header at full stretch and the goalkeeper saved at the feet of MacDonald soon after.
David Perkins had a shot blocked for the hosts as they started to come back into it but Brentford deserved to be ahead - and took the lead just before the half hour.
Alexander worked hard to win a corner and when Saunders lifted it in it dropped loose and the powerful striker rifled in his sixth of the season from close range.
It was almost two soon after when MacDonald laid off an Alexander flick into the path of Saunders but the shot dribbled wide.
Lee saved a curling Kayode Odejayi shot and Stephen Wright blocked an Ashley Vincent effort but Alexander almost doubled his tally at the other end with a looping header that landed on the roof of the net.
Colchester were playing a direct style in an attempt to force their way back into the game and they almost got a leveller when Brentford failed to clear and Odejayi shot low but Lee saved.
The home side had the better of the later stages of the first half after being second best for most of it.
Ashley Vincent, switched to the left in an attempt to get more involved in proceedings, shot over from a tight angle as half time approached but The Bees went in ahead.
And having weathered that storm before the break, and re-shaped slightly to keep Vincent quieter, Brentford started the second half in the same vein they played most of the first.
They could have been two up when Marcus Bean nodded a superb Saunders cross inches wide, and had the better of early possession and territory.
Lee was forced into action to hold a near post Brian Wilson shot and then saved low when a Vincent shot deflected off Alexander.
The hosts began to come into it and David Perkins shot wide from the edge of the box and they pressed for a leveller.
The game was see-sawing, with one team having the better of it and then the other, but Brentford's spells were longer and more productive.
Goalkeeper Williams almost presented the visitors with a second goal when he missed a Saunders corner but Legge was caught unawares and the ball hit him and went wide.
The home side came close to levelling when they broke the Brentford line twice in quick succession, firstly Wright made a fine tackle to deny the on-running Andy Bond before Lee saved at the feet of Vincent moments later.
Saunders shot wide on the turn before the game descended into farce soon after.
Myles Weston, introduced as a substitute, pulled up injured and crumpled into a heap on the side of the pitch.
Referee Dave Foster allowed the game to continue and Lee saved superbly from Liam Henderson after a good move down the right against an understrength Bees.
The ball went dead soon after but Mr Foster allowed Colchester to continue and then awarded a free kick on the edge of the penalty area when the offence may have been inside.
With Brentford still unable to make their substitution, Liam Henderson fired the free kick into the wall and Bond shot wide, giving The Bees a chance to re-group - albeit with Weston now off.
And they sealed the win with a superb second goal in stoppage time.
Alexander - in his last action of the night - fed the overlapping Michael Spillane, he played the ball across the box and MacDonald arrived to seal the win and send Brentford home delighted and with the points.
Colchester United: Williams; Wilson, Reid, Baldwin, Tierney; Vincent, Bond, Perkins, I. Henderson (sub Wordsworth 85 mins); Odejayi (sub L. Henderson 63 mins), Mooney
Subs (not used): Cousins, Beevers, White, James, Heath
Brentford: Lee; Wright, Legge, Osborne, Woodman; Bean, O'Connor, Diagouraga (sub Weston 65 mins (sub Spillane 82 mins)), Saunders; MacDonald, Alexander (sub Simpson 90 mins)
Subs (not used): Hamer, Balkestein, Hunt, Forster
Bookings: Woodman (84 mins) (third of season)
By Chris Wickham