Montell Moore's sublime double helps Development Squad to first league win under Lee CarsleyLee Carsley's secured his first U21 Professional Development League Two South win as manager which, in the process, moved The Bees off the foot of the table at the expense of their West Country opponents.
City took the lead, against the run of play, after a quarter of an hour as Raphaël Calvet put through his own goal under pressure from Jamie Horgan.
The Bees weren't behind for long as Montell Moore curled a fine equaliser seven mintues later before Daniel O'Shaughnessy's header evaded Dave Richards grasp to put Brentford ahead.
Sam Saunders fired home an unstoppable free-kick two minutes before half-time and the game was wrapped up midway through the second-half as Jermaine Udumaga converted from the spot.
Moore put the icing on the cake with the pick of the afternoon's goals as he exchanged passes with Louis Hutton and volleyed across Richards and into the far corner of the net to complete the scoring seven minutes from time.
Lee made six changes from last Monday's draw with Colchester United as James Tarkowski, Calvet, Tyrell Mitford, Nico Yennaris, Courtney Senior and Saunders all started.
From the outset Brentford dominated possession while The Robins, who started the day three points better off in the table, looked to release the pacey Matthew Mattis at every opportunity.
The visitors played with three centre-backs while Jordan Wynter and Lewis Hall pushed on as wing-backs but, against the lone Bees striker in the form of Mitford, for most of the opening half two of the defenders were marking open space while Brentford overloaded the central midfield area.
Tarkowski headed over from a Saunders corner and Yennaris' saw deflected shot turned over by Richards as Carsley's side bossed the opening stages.
Richards made a good save to deny Moore before the visitors took the lead with their first real foray into Brentford territory.
Joe Morrell turned Udamaga in the midfield and delivered a teasing cross which Calvet could only turn into his own net with Jamie Horgan and Mattis waiting to tap the ball home.
For a side that had gone nearly three months without a win that goal could have knocked The Bees confidence but they responded well and were level seven minutes later.
Udumaga's ball down the right was kept in by Courtney Senior and he pulled back to Moore just inside the box who twisted and turned before cutting onto his left foot and curling past Richards from 15 yards into the far corner.
Things got even better for Lee's side just after the half-hour as Moore's cross was bundled behind by a combination of Wynter and Richards and from the resulting corner Daniel O'Shaughnessy rose highest and his header beat Richards from eight yards, although the City 'keeper will feel he should have kept it out.
By now the game had descended into a frantic scrappy affair with the pitch, which was played on Saturday in the Youth Team's win over Ipswich Town, starting to cut up after yesterday's torrential rain.
Tarkowski and O'Shaughnessy were comfortably dealing with the long-balls coming their way meaning City were finding it very difficult to get up the pitch while City's three central defenders and defensive midfielder meant space around the box was at a premium for Brentford.
It looked like Brentford would go into the break with a one-goal lead but their advantage was doubled on the stroke of half-time as Saunders whipped an unstoppable free-kick from just right of centre over the wall and into the far corner to give The Bees breathing space.
The opening-half hour of the second-half went much the same way as the first with plenty of battling play in the midfield but aside from a Moore shot straight at Richards neither goal looked under any threat.
That all changed with 20 minutes to go as Adam El-Abd hauled down Tarkowski as he went to attack a Saunders' corner: the referee pointed to the spot and Udamaga placed the spot kick high to Richards right to make it four.
Jack Bonham had barely been needed all afternoon but he was finally called into action with a quarter of an hour to go dealing with a pair of regulation shots from Billy Murphy and Liam Monelle.
El-Abd made up for his error in giving the penalty away by making a strong block to turn away Udamaga's shot and trialist Shaun McCloskey should have done better with his header from Yennaris' inviting centre.
Brentford did get a fifth with seven minutes to go as Moore scored the pick of the days goals and, given the quality of his first and Saunders' free-kick, that was no mean feat.
The 18-year-old exchanged a one-two with Louis Hutton from a corner on the right-hand side before volleying the return pass into the far top corner from the edge of the box level with the penalty spot.
Connor Lemonhaigh-Evans was denied by Bonham while The Bees almost added a sixth in the dying seconds but McCloskey's curling effort drifted the wrong side of the post.
As it was Lee Carsley's side picked up their first win under the former Everton man to move off the bottom of the table ahead of next Tuesday's West London derby with QPR.
Brentford DS: Jack Bonham; Raphael Calvet, James Tarkowski, Daniel O'Shaugnessy, Aaron Greene; Nico Yennaris; Sam Saunders (sub Louis Hutton 75 mins), Jermaine Udamaga, Courtney Senior, Montell Moore; Tyrell Mitford(sub Shaun McCloskey 55 mins)
Subs not used: Mark Smith, Bradley Clayton, Tom Field
Bristol City DS: Dave Richards; Jordan Wynter, Zak Vyner, Adam El-Abd, Lewis Hall; Zak Batten, Ben Last (sub Conor Lemonhaigh-Evands 59 mins), Joe Morrell, Billy Murphy; Matthew Mattis (sub Liam Monelle 73 mins), Jamie Horgan
Subs not used: Jojo Wollacott, Ben Withey, Jack Andrews