A first-half strike from Bradley Ihoinvien successfully paved the way for the U's into the knockout stages of the Bristol Street Motors Trophy.
Matty Etherington made five changes to the side that lost at Stockport on Saturday, with Tom Smith, Fiacre Kelleher, Tom Hopper, Chay Cooper and Brad Ihionvien all coming into the starting XI.
One point was needed to guarantee our place in the next round of the Bristol Street Motors Trophy ahead of Tottenham Under-21s and Cambridge.
The first half was a very even affair with both sides enjoying spells of possession but struggling to break the other down.
Cooper had the biggest chance for the U’s, breaking through on goal and forcing a fine double save from Fynn Talley to prevent an opener.
Ten minutes later, Colchester had the lead. Cooper drilled a ball across the box and it looked to be travelling towards the safe hands of the goalkeeper. But the man in net spilled the ball out towards Ihionvien who hit a shot first time into the back of the net, giving his side the lead.
The second half was largely dominated by the home side, who fashioned plenty of chances down both flanks – in particular with Jayden Fevrier, who came on as a sub for the injured Jay Mingi.
A number of changes were made in the second half to try and maintain our grip on the game while Peterborough threw on plenty of attackers in search of an equaliser.
Emmanuel Fernandez skewed a massive opportunity for the visitors in stoppage time, but the defender poked his effort wide of a stranded Smith in goal.
Visitors Peterborough fielded a young team having already secured their qualification, presenting the U’s with a good opportunity play on the front foot and dominate the game.
But it was the away side who started with more aggression, twice testing Smith in goal as Colchester looked to find their feet at the Jobserve Community Stadium.
Ten minutes into the match Etherington’s men put together their first good move, playing around the Posh boys on the edge of their box but unable to get a shot away on goal.
Ihionvien had a good opportunity on nineteen minutes, forcing Talley to spill the ball with his shot but the goalkeeper was able to recover and prevent the ball from falling into the back of the net.
The striker would soon after require treatment on the pitch having been caught in the face, but the youngster was able to get back up and continue on.
Cooper then went closest to opening the scoring thirty-five minutes in, beating the offside trap and bearing down on goal, but fluffing to efforts inside the box.
Approaching half-time, Mingi picked up a knock that forced him off and Fevrier was the man called back to replace him.
But before he could enter the action, ten-men Colchester took the lead through Ihionvien who pounced on a loose ball from the goalkeeper and rifled home.
Will Greenidge was next to test the keeper with a low effort but this time Talley was equal to the strike and prevented a second for the U’s.
Ihionvien, brimming with confidence, then tried a long-ranged effort having seen the keeper off his line, but the stopper was able to retreat quickly enough to keep the floated shot out just before the half-time whistle sounded.
One change from Etherington at the break saw Arthur Read make way for Cameron McGeehan in an effort to freshen legs up in the middle of the park.
Play continued in a similar manner to how the first half ended, with the U’s in control of the ball and fashioning regular chances.
Noah Chilvers almost got a dangerous free-kick over the wall and on target, but his effort needed a bit more lift.
Mandela Egbo then had a chance, dancing through the Peterborough defence but pulling his shot just wide.
The Posh then had a chance of their own, Malik Mothersille got on the end of a low cross and cannoned his effort back off the post.
The loose ball was then picked up by the U’s who broke through Cooper. The winger was able to speed down the line and dink a ball into the box and an arriving Chilvers could only poke his shot wide on the stretch.
Greenidge was in action at the other end with half an hour to play, throwing himself as a Peterborough cross and preventing Mothersille from tapping home first time.
Romoney Crichlow was the first man into the book in North Essex, picking up a caution for a challenge on Fevrier in his own half.
David Ajiboye almost levelled proceedings with a thunderous strike on the edge of the penalty box, but his dipping strike went over the bar and into the North Stand.
Two more changes from the boss saw Kelleher and Chilvers both depart, to be replaced by Gene Kennedy and Frankie Terry for the final twenty minutes.
Kennedy was soon in the book for a cynical foul that prevented the visitors from breaking.
Egbo was the next to be withdrawn with Barrow on Saturday in mind – Donell Thomas was introduced and the U’s reverted to a back five to try and see the game out.
Posh sub Will Van Lier was another player to be cautioned by the referee for a tactical foul that stopped the hosts from mounting an attack.
As the clock continued to tick, the game became more open with the U’s pushing for a second goal and Peterborough searching for an equaliser.
Fernandez had a huge chance to level things at the death but somehow failed to pass the ball into the net with no pressure on him.
And after four minutes of added time, the U’s walked away as 1-0 winners and were safely through to the next round of the Bristol Street Motors Trophy.
Colchester XI: Smith, Greenidge, Kelleher (Terry, 70), Chilvers (Kennedy, 70), Hopper, Mitchell, Read (McGeehan, 46), Egbo (Thomas, 76), Mingi (Fevrier, 42), Cooper, Ihionvien
Subs: Goodman, McGeehan, Kennedy, Nelson, Thomas, Terry, Fevrier
Peterborough XI: Talley, Crichlow, Fuchs (O’Connell, 46), Havilland, Sturge, Ajiboye, Mothersille, Fernandez, O’Brien-Brady (Corbett, 57), Dornelly, Mills (Van Lier, 67)
Subs: West, Corbett, O’Connell, Van Lier, Unwin, Davies, Gilbert