The U’s made four changes for the game at Griffin Park, with Eastman, Coker, Izzet and Henderson coming in for Rose, Heath, Duguid (injured) and Morrison, with the three available players dropping to the bench.
As those chances became less frequent in the second half, it looked like the U's hard work would at least garner them a point to take home from West London, but a late Farid El Alagui header grabbed the win for Uwe Rosler's side.
After the disappointments of Tranmere last week, the U's were more resolute this time and had good chances of their own to try and win the game.
There was late heartbreak for the U's at Griffin Park on Saturday as a late Brentford goal condemned them to a second successive defeat for the first time since November 2011.
The first chance of the game came on four minutes, as a ball in from the right found Donaldson eight yards out from goal, but he was always stretching for a header and it went over the bar.
The home side had a great chance then on ten minutes as Diagouraga was put in on the counter attack by Donaldson, but he pulled his shot past the near post and wide of Cousins goal.
The game was a fairly open one when the two teams got their passing game going – first Henderson was denied a shot on goal by the outrushing Moore, before Donaldson wasted another great chance by firing wildly over.
The U’s were not adverse to getting the ball into the area and from one whipped ball from right to left, Bond was just unable to help it back across the goal and past Moore.
Shortly afterwards, Henderson darted away down the left and checked back to send in a cross to the far post, which Wordsworth glanced just wide of the far upright.
At the other end, Forshaw drilled a shot-cum-cross just past the far post, before the U’s almost profited from another sloppy backpass from the home defence.
Sears almost got in, but Moore was sharp to ensure that he clipped the ball away from the striker’s feet.
A Bean counter attack allowed him to get it to Sears and he set up Wordsworth, whose drilled shot was well blocked.
Not long after, Henderson broke the offside trap with a ball over the top but he could only find the legs of Moore who stood up well.
The U’s front man went close again on 32 minutes, making the most of a rebound from a Sears through ball to shoot, only to drag his shot agonisingly wide.
Logan saw a shot from distance go just as close to going in, deflected narrowly wide, before the U’s defended manfully to get the resulting corner away, along with a pair of set pieces after that.
There were chances aplenty, the U’s next to go close just before the interval having ridden some Brentford pressure.
A free kick deep on the right was swung in and Eastman got up highest, but couldn’t quite power his header on target.
The second half started off in just as frenetic fashion.
The Bees were denied a penalty shout as Douglas went to ground with Wordsworth in close proximity and the U’s hit their opponents on the counter.
Henderson got to the edge of the box and slid in Sears, who found Moore quickly bearing down on him.
A good spell for the U’s ended with the Bees on the counter, as Donaldson spun Okuonghae and Wilson on the halfway line and bore down on goal.
He seemed destined to get a shot away, but Wilson did just enough to put him off and Cousins gathered.
The U’s shot stopper then pulled off a sensational save. Logan swung a ball across the six yard box which was met by the sliding Douglas, but Cousins blocked with his feet with a brilliant save.
The chances dried up somewhat after that – although the game continued to swing back and forth as the teams looked for a goal.
The home side had the next sight of goal as Cousins cleared the ball straight to the feet of El Alagui but stood strong as the striker arrived in the box to turn the shot away.
The U’s keeper could do little about it when the home side took the lead in the last five minutes of the match.
The ball was swung in from the right hand byline and El Alagui – who had missed some great chances earlier in the game – dived to bury the header past the helpless U’s keeper.
U's: Cousins, Wilson, Okuonghae, Eastman, Coker; Bond, Izzet, Bean; Wordsworth (Morrison 88); Sears, Henderson
Subs not used: Pentney, Rose, Heath, White, Sanderson, Massey