Anthony Wordsworth fired in a superb free kick to give Colchester United a scarcely deserved point in a 1-1 draw at Griffin Park.
Clayton Donaldson looked as if he would be Brentford's match winner when he gave them the lead early in the second half and they held it against ten men in to stoppage time.
The hosts would have deserved their third successive 1-0 win but Wordsworth curled in a leveller in the dying seconds to give the Essex side a share of the spoils.
The Bees had much the better of the first half without taking the lead but did so soon after the re-start and Colchester rarely threatened until their last minute leveller.
The first 15 minutes was lively, both teams had openings without creating the opening goal.
Michail Antonio blazed well over for the visitors before a Myles Weston cross just eluded Niall McGinn.
Miguel Llera, making his full début at the hear of Brentford's defence, was causing the visitors problems with his passing and from one delightful ball down the line McGinn cut inside and bore down on goal, but the wide man couldn't get a shot away and the chance was gone.
Marcus Bean blocked a Kem Izzet shot before McGinn curled an effort over the top and an Ian Henderson shot flew across the face of goal.
As the half wore on Brentford began to take control and their best moves were starting on the left side of their defence with Llera spraying inch perfect 60 yard passes and Blair Adams, on his Football League début, bursting forward to great effect.
The Sunderland loanee set up a chance for McGinn after one run but the shot curled inches wide of the far post and moments later Bean's volley from an Adams cross forced Mark Cousins in to a brilliant save.
Weston forced a low save out of the Colchester goalkeeper after picking up one Llera pass and from a similar ball Weston fed Adam Thompson and Jonathan Douglas volleyed the cross narrowly wide.
It was almost a chance a minute for the home side, but they couldn't find the breakthrough.
McGinn had a shot blocked after a short corner, Weston fired inches wide after intercepting a Lloyd James pass and Cousins held on to a Douglas header.
The Bees had appeals for a penalty when Donaldson and Magnus Okuonghae came together in the penalty area when trying to reach an Adams cross but referee Gavin Ward ruled no offence had been committed.
McGinn fired across the face of goal in the closing stages of the first half but Colchester went in level at the break and would have known they were lucky to be.
It was almost even better for the Essex club, a Henderson cross was half cleared and Antonio shot wide from the edge of the penalty area with the goal gaping.
The visitors improved in the early stages of the second half and Lee had to tip a fierce Henderson shot over the bar to prevent them taking an undeserved lead.
Okuonghae lifted an effort on to the roof of the net and Antonio fired well wide while at the other end Douglas had a shot blocked and Donaldson fired an effort across the box that Colchester managed to scramble away.
The goal Brentford deserved came ten minutes in to the second half, Douglas won the ball on the edge of his own penalty area as Colchester attacked and seconds later the ball was in the net at the other end.
The Bees midfielder fed Weston and he threaded a pass for Donaldson to run on to, he muscled his way past Okuonghae and finished low past Cousins.
Weston could have doubled the lead moments later but his shot was saved by Cousins and Llera fired a free kick well over.
Colchester should have equalised with 20 minutes remaining when Brentford failed to deal with a long ball and Henderson fed it inside to Steven Gillespie but the substitutes volley was weak and Lee was able to palm it away.
The game was more even after the break, despite Brentford's goal, and there were fewer chances.
Weston curled an effort wide and Karleigh Osborne missed the target with a volley as Brentford had the better of it, but not emphatically so.
The Bees were handed an advantage for the final ten minutes when Colchester substitute John-Joe O'Toole was sent off for a horrible tackle on Weston and Douglas could have wrapped the game up moments later when McGinn burst clear and found him on the edge of the box - the midfielder's first shot was blocked and his second was saved by Cousins.
Wordsworth shot narrowly wide as Colchester sought a leveller while the visitors blocked a Donaldson effort after good work by Mike Grella.
The visitors equalised as the game ticked past the 90 minutes and that proved to be enough.
Osborne volleyed wide and Kevin O'Connor had a looping header saved but Brentford couldn't find a way through and the game ended level.
Brentford: Lee; Thompson, Osborne, Llera, Adams (sub Wood 66 mins); Bean, Reeves (sub O'Connor 73 mins), Douglas; Weston (sub Grella 86 mins), Donaldson, McGinn
Subs (not used): Moore, Eger
Bookings: Thompson (35 mins) (second of season)
Colchester United: Cousins; Wilson, Okuonghae, Heath, Coker; Wordsworth, Izzet (sub O'Toole 63 mins), James; Henderson, Odejayi (sub Bond 77 mins), Antonio (sub Gillespie 63 mins)
Subs (not used): Baldwin, Duguid
Bookings: Wordsworth (12 mins), Heath (78 mins), James (90 mins)
Sent Off: O'Toole (81 mins)
Attendance: 4,714 (183 away fans)
By Chris Wickham