Shaquille McDonald, Jaanai Gordon and Peter Grant scored the goals as the under 21s progressed into round two of competition.Peterborough United made it into round two of the Premier League under 21 Cup following a hard-fought 3-2 win over Colchester United at London Road, with Bristol City the next opponents in the competition for Gavin Strachan's men.
The deadlock was broken on nine minutes as a long clearance from goalkeeper Alex Lynch was latched onto by teenage front man Shaquille MCDONALD, who bravely headed past Phillips with the ball finding the back of the net via the underside of the upright.
Fagbohun was denied by Lynch moments later before Jaanai Gordon dragged a shot wide of the post after cutting inside from the left.
The visitors found the equaliser just before the quarter hour mark as some slack defending allowed FAGBOHUN to cut inside and fire a low drive past the despairing dive of Lynch.
McDonald immediately found the back of the net with a clinical finish, but the offside flag curtailed the celebrations.
The U's made it 2-1 on 25 minutes and it was FAGBOHUN again who found the back of the net, guiding a header past Lynch following a good cross from Simmons.
On 27 minutes, Posh levelled the scores as a corner from Tom Conlon was nodded home at the near post by skipper Peter GRANT. McDonald saw a left-footed effort saved by Phillips after good work from Brown on 38 minutes.
On the stroke of half-time, Posh got their noses in front as good pressing from Brown and a subsequent pass to GORDON was clinically finished by the teenager who has been a regular on the substitutes bench for the first team this term.
Sanderson was superbly denied by Lynch moments after the re-start, the goalkeeper pushing a fierce free-kick around the post. Lynch denied Fagbohun moments later with his legs as Colchester made a bright start to the second period.
At the other end, some powerful play from Gordon saw him burst into the box, but his volley was parried by goalkeeper Bransgove. Carthey fired wide of the near post after more good work from the industrious Brown in midfield.
Shaquille McDonald was denied his second goal of the afternoon by a fine save from Bransgove after the front man had outjumped his marker at the far post.
Jack Simmons fired wide of the near post after a tricky run into the box as the game entered the final stages at a sunny London Road.
Goalkeeper Bransgrove produced a world-class save in the dying moments to deny a volley from McDonald as Posh clinched a spot in round two of the Under 21 Premier League Cup.
Posh: Lynch, Richens, Marshall, Conlon, Trialist, Grant, Ward, Carthey (sub Burgess 78min), McDonald, Gordon (sub Edwards 88min), Brown. Unused subs: O'Reilly, Phillips, Duggan.
Colchester: Phillips (sub Bransgrove 46min), Melaugh, Sanderson, Roast, Curtis, Smzodics, Simmons, Fagbohun, Ladapo, Nwachuku, Andrews (sub James 79min). Unused subs: Monk, Harrison, Issa.