The 18-year-old rapped up a comfortable win for Barry Fry's side when he slammed in a remarkable twenty-yard drive in the last minute of the game.
The Posh had dominated the match and thoroughly deserved their victory which puts them up to tenth in the fledling Division Two table.
Brentford's starting line-up was boosted by the presence of Anthony Rougier who was making his Bees debut. The veteran Trinidad & Tobagan signed a three month contract on Friday, having ignored advances from Brighton.
But Rougier's Brentford career got off to the worst possible start when Peterborough took the lead in the second minute. Former Wimbledon striker Andy Clarke capitalised on a long kick out from Boro 'keeper Mark Tyler to score.
The Bees hustled and bustled in search of an equaliser throughout the first period but received no reward, indeed, an in form Leon McKenzie would almost certainly have put the visitors further in front. However, a lack of confidence in front of goal ensured the score remained at 1-0.
Just after half time Peterborough doubled their advantage. Mark Arber found the net from close range after the usually reliable Brentford stopper Paul Smith fumbled a cross.
With the home side all but resigned to defeat the second half was something of a non-event, enlightened only by the moment of magic from Reading's Andre Boucard. Showing great composure, Boucs rolled the ball back and calmly lofted a shot beyond the keeper and into the back of the net to the delight of the Peterborough traveling faithful.
Boucard is a huge favourite amongst Peterborough supporters after a previous successful loan tenure at the end of last season. Another astounding performance from the young prodigy yesterday will go to further enhance his reputation.
Barry Fry, Peterborough manager, revealed after the game that he was hardly surprised to see Boucard score his first Boro goal in such spectacular fashion.
"I am delighted for Andre who made it 3-0 in the dying moments. He does that in training and I have been telling him to do it in the game and he made me eat my words, it was a great strike and made the score-line comfortable," he commented.
Boucard meanwhile was simply beaming as his last minute strike was the first goal of his tender professional career.
"I am very pleased to score my first goal for Posh," he said, speaking to the press after the game.
"After that strike, I hope it is the first of many because I really enjoyed the moment.
'The game itself involved a lot of battling as it was tough out there, but our quality came out on top and we showed them how football should be played. I enjoyed the game and I am looking forward to next week's game against Sheffield Wednesday," he added.
Elsewhere, Colchester lost 1-0 to Swindon. The U's, managed by Reading legend Phil Parkinson, went down to a late strike from Tommy Mooney. Swindon, who say they are aiming at promotion this season, included former Reading stars Sammy Igoe and Adi Viveash in their side.