The Bees fought back and produced a spirited display, but some defensive lapses meant a clinical Stevenage side would earn the win.
Neil MacFarlane was able to call on Mads Bidstrup for the first time this season as he continued his recovery from a long-term injury to get 60 minutes under his belt. Gustav Mogensen also earned his first start following his injury comeback too.
It was a tough start for the young Bees as Stevenage started brightly, and they went ahead on six minutes when Elliott Osbourne hit a powerful attempt from distance which caught out Jared Thompson to end up in the back of the net.
Despite falling behind, Brentford B began to gain their passing rhythm and almost hit back on 14 minutes when a Fin Stevens cross found Mogensen, who curled an effort towards the far corner, but for a good save from the keeper. The resulting corner then led to a chance for Kane O’Connor, but he headed just over.
Moments later Mogensen would have another effort well saved before Aaron Pressley saw his close-range attempt blocked on the line as Stevenage cleared.
The Bees would regret those missed chances as they fell further behind when a long ball over the top caught out the back line before Harry Draper latched onto the ball, and to his credit, finished with precision.
Just one minute later, though, Brentford B would be back in the match when Fin Stevens netted his first goal for the Club with a powerful drive from distance. After Lachlan Brook attempted first, the right back smashed home to round off a move which featured some excellent build-up play from Mogensen.
Neil MacFarlane’s side continued to dominate possession but Stevenage carried a real threat on the counter-attack, and the side were given a couple of warning signs when Liam Smythe fired wide, but his third chance saw him shoot earlier this time as he found Stevenage’s third from the edge of the box.
A couple of half-time changes saw Wraynel Hercules and Ben Winterbottom introduced, with the latter earning his first outing for the young Bees. The rhythm of the match continued much the same as the first half as the likes of Bidstrup and Alex Gilbert continued to see lots of the ball, and a good chance came on the hour mark when Lewis Gordon raced down the left before his low cross evaded the onrushing forwards.
The side kept pressing for a way back into the match, and with the introduction of three Trialists and Valgeir Valgeirsson, the second Brentford goal arrived on 72 minutes. Good wing play from Hercules saw him play an excellent ball low into the box after beating his man, and Pressley was on hand to fire home first time.
The momentum stayed with The Bees and an equaliser did arrive on 81 minutes when Gilbert fired home from distance after more incisive play from Brentford as they deservedly made it 3-3.
But the lapses which had hampered them earlier in the game once again occurred as a long ball over the top wasn’t dealt with and Smythe kept his composure to grab his second of the night- and ultimately the winner- two minutes from time.
Brentford B: Thompson (Winterbottom, 45) Stevens (Trialist, 60) Gordon, O'Connor (Valgeirsson, 60) Bidstrup (Trialist, 60) Pressley, Gilbert, Mogensen (Trialist, 60) Brook (Hercules, 45) Hockenhull (Robb, 78), Crama
Subs not used: Koutsimouka, Carre
Stevenage XI: Johnson, Bunyan, O'Keefe, Williams, Lontton, Tamplin, Osbourne, Draper, Smyth, Bancroft, Dreyer
Subs: Campbell-Ryce, Smith, Arai, Onyeagwara, Collard