Luke Chambers first half double ensured that the U's would be in the draw for the last sixteen of the Papa John's Trophy with a 2-1 win at Swindon Town.
Chambers was the unlikely two-goal hero against the Robins, netting both goals inside the opening eleven minutes of the game.
Romoney Crichlow made it 2-1 in firs half stoppage time, but the U's were able to shut out the home side for the duration of the second half, and ensure they would be in the draw for the last sixteen of the tournament.
Colchester United opted for two changes for their Papa John's Trophy Round of 32 game at the County Ground against Swindon Town.
Coming into the starting eleven were Miles Welch-Hayes and Alan Judge, in place of Luke Hannant and Charlie Daniels. Notable absentees for the U's were Frank Nouble and Tom Eastman who were both missing through injury.
The U's made a brilliant start to the tie, racing into a two-goal lead in the opening eleven minutes at Swindon Town, with Luke Chambers netting both for Colchester United.
After Jake Turner's immaculate ball was collected by Armando Dobra, the on-loan forward won a corner for the U's in the fifth minute. And Alan Judge's deliveries were proving too much for the Robins' defence, with Tommy Smith's initial effort deflected behind. Judge almost curled the ball into the far post, but for a touch from Ward, but it was from the third U's corner that the visitors toook the lead.
Alan Judge's cross looked destined for Chambers' head from the moment it left his boot, with the centre back nodding in easily at the back post with five minutes played.
And Chambers made it 2-0 to his side six minutes later. It was a different delivery from Judge this time, an outswinging free kick from the edge of the box, with the centre back nodding the ball across the face of goal and into the far corner of the net.
The chances kept coming for the U's, with Sears having an effort blocked by Ward, before Jasper Dobra and Chilvers all got in the way of eachother from Judge's good ball in, spurning a good chance in front of goal.
Luke Chambers went close to completing his hattrick after twenty-six minutes when his flicked header had to be cleared in the six-yard area from one of the U's many corners in the first half.
But just before the break, the home side grabbed one goal back, with Romoney Crichlow on target for the home side. His header nestled in the far corner after a good delivery, cutting the U's lead in half just moments before the break.
Noah Chilvers was the first to force a save out of Lewis Ward in the second half, cutting in from the left wing to drive into the penalty area. His low effort was well held by the Swindon 'keeper ono a slippery evening, with Sears closing in.
The U's were having to soak up a lot of pressure from the home side, as Swindon Town looked to grab an all important equaliser, but the defensive partnership of Chambers and Smith were doing well at controlling the back line.
And chances did come for the U's at the other end of the pitch, but they were unable to capitalise on them, with Samson Tovide firing just wide of the mark after a neat ball through from McCoulsky.
Luke Chambers put in an excellent goal-saving tackle with ten minutes to play after Alex Gilbert had got the better of Miles Welch-Hayes. The centre-half managed to get back across and block the effort from Mitchell-Lawson and deny an almost certain goal.
But the U's were able to hold on and claim a place in the last sixteen of the Papa John's Trophy, with a 2-1 victory at the County Ground.
Up next for Hayden Mullins' side, a home tie in the Emirates FA Cup on Sunday afternoon against League One Wigan Athletic.
Swindon Town starting XI: Ward, Crichlow, Lyden, McKirdy (Fox 63'), Mitchell-Lawson, Gilbert, East, Dabre, Francis (Gordon 57'), Minturn (Dworzak 88'), Grant.
Unused subs: Mildenhall, Winchcombe, Wynn-Davis, Bunch.
Colchester United starting XI: Turner, Welch-Hayes, Chambers, Smith, Skuse, Judge (Hannant 64'), Sears (McCoulsky 64'), Chilvers, Jasper (Tovide 64'), Dobra (Tchamadeu 87'), Coxe.
Unused subs: Gerken, Daniels, Cooper.