Colchester 3 (Massey 62, Murphy 80, Moncur 86)
Reds 1 (Waring 40)
Barnsley threw away the points at relegation-strugglers Colchester United and their Play-Off hopes were smashed in the second half at the Weston Homes Community Stadium.
After a first half of complete domination, it looked like there was only going to be one winner but a disappointing second half cost Lee Johnson's side.
It was a frantic but tight opening as both sides looking to give nothing away in the opening exchanges. With eight gone, the first shot was registered by Conor Hourihane but he saw his effort blocked on the edge of the box.
A low ball in from Lalkovic was begging to be turned home but no yellow shirt was on hand as the home side cleared on 12 minutes.
Barnsley were enjoying the majority of play and almost found an opener in bizarre circumstances as Mason Holgate's cross almost caught Walker out but the United 'keeper turned it over for a corner.
The Reds were probing the Colchester back line with relative ease and Conor Hourihane's pull-back on 26 minutes was ripe for smashing into the net but again no Barnsley shirt was in sight.
Barnsley's play had everything but a goal as they probed with patience against the League One strugglers. Waring came close to nodding Barnsley in front as a floated delivery was knocked into the box but it was just too high for the Stoke loanee.
On 40 minutes, however, Waring did claim Barnsley's opener - the least they deserved. Hourihane's delivery cause mayhem in the Colchester box and Waring seemed to get the last touch to turn just over the line.
It was a case of picking up where they left off from the first half for Lee Johnson's side. Three minutes into the second period saw the U's forced to clear another deadly Hourihane delivery with Waring and Lalkovic lurking.
With 51 played, Hourihane took aim at a bouncing clearance from Khumalo but he sliced his strike over the bar from the edge of the area.
Colchester had to decent chances in quick succession. Porter smashed towards the near post on 55 but the returning 'keeper punched behind. From the subsequent corner, Alex Wynter's pointblank header was straight at Davies - who was eternally grateful the effort wasn't sent either side.
Two minutes before the hour, Milan Lalkovic jinked his way into the area before hammering low at goal. His effort was blocked into the path of Pearson on the edge of the box but his strike was expertly turned out for a corner by Walker.
The home side were given a lifeline on 62 minutes as Gavin Massey latched on to Jacob Murphy's cross to turn home for 1-1. It came completely out of the blue.
Josh Scowen took matters into his own hands on 68 minutes as he charged into the box past five players but was prevented from connecting properly and scoring what would have been a sublime goal.
On 72 minutes the Reds could have notched their second through Pearson once more but Eastman got a great block in to deny the Manchester United loanee - Waring was the architect as he teed up his team-mate on the edge of the box.
With only 10 minutes left, Colchester took the lead as Jacob Murphy had the goal at his mercy to head into an empty net.
Sam Winnall thought he'd levelled the tie on 85 minutes when he latched on to Nyatanga's threaded pass in the box and rounded the 'keeper to tap home but was denied by the flag.
From one end to the other, Colchester sealed the tie on 86 minutes when Massey pulled back for Moncur to hammer home. It went from complete to domination to disarray for Barnsley.
Colchester: Walker, Brindley, Khumalo, Eastman, Wynter; Moncur, Szmodics (Gilbey 56), Lapslie; Massey, Murphy, Porter.
Subs: Lewington, Vincent-Young, Harney, Gilbey, Healey, Bonne, Sembie-Ferris.
Reds: Davies, Holgate, Cranie, Nyatanga, John, Bailey (Winnall 76), Pearson, Hourihane (Berry 86), Scowen, Lalkovic (Stewart 70), Waring.
Subs: Dibble, Smith, Ramage, Hemmings.
Referee: Mr K. Hill.
Attendance: 5,157 (699 Reds).