Reds put in a battling performance but Forest prove too strong for Paul Heckingbottom's side.
Barnsley battled strongly but a clinical Nottingham Forest proved too strong for the Reds, running out 5-2 winners under the lights at Oakwell.
James Bree swung in a sensational cross which Sam Winnall headed home for the opener five minutes in, but Henri Lansbury levelled the game with a venomous free kick.
Forest were level for just over a minute before Conor Hourihane chipped the ball into the path of Marley Watkins, who tucked home unopposed, but a scrappy Apostolos Vellios goal tied the game up again soon after.
Adam Hammill twice came close to putting the Reds back ahead only for Lansbury’s stoppage time header to edge Forest ahead at the interval.
Winnall twice came close to levelling shortly after the restart before Ben Osborn flicked home Michael Mancienne’s cross shortly after the hour.
Things went from bad to worse for the Reds when Marley Watkins was sent off for an incident involving Thomas Lam and Lansbury completed his treble with a penalty eight minutes from time after Josh Scowen felled Matty Cash.
The Reds started by far the strong of the two sides and took the lead inside five minutes.
James Bree, on his 50th Reds appearance, showed his raw speed and broke clear down the right, leaving left-back Danny Fox chasing his shadow.
He then delivered a perfect cross into the area, which Sam Winnall glanced home from close range.
With the game barely 10 minutes old, Adam Hammill swung in an inviting free kick for Adam Jackson, who stooped to meet the cross, only for the ball to loop onto the roof of Vladimir Stojkovic.
Three minutes later, the visitors levelled as Henri Lansbury fired home a free kick from 25 yards after being teed up by Pajtim Kasami, but they were level for little over a minute.
The Reds went straight back on the offensive and Conor Hourihane’s delicate chip was superbly controlled by Marley Watkins and dispatched with real venom.
Ben Osborn tried his best to pull the visitors level with a driven effort that was comfortably gathered by Adam Davies, but the Reds stopper was unfortunate to be beaten again midway through the half.
Fox’s low ball in from the left was squirmed home by Apostolos Vellios with some help from the underside of the crossbar.
Adam Hammill bent a free kick over the top for Barnsley as the Reds went in search of a third goal, with Adam Armstong’s strong run and deflected effort turned on target by Winnall, but he failed to test Stojkovic.
A clever corner routine from Conor Hourihane saw a drilled ball catch the visiting defence cold but Sam Winnall driven effort was turned away by Stojkovic before Hammill drove down the right but his outside of the foot shot was well saved.
Two minutes before the break, Marc Roberts’ long throw broke to the edge of the area but Hammill was unable to keep his effort low as it fizzed over the crossbar.
The visitors took the lead for the first time in the match in stoppage time as Ben Osborn’s cross was headed just out of Adam Davies’ reach by Lansbury.
HALF TIME: Barnsley 2-3 Nottingham Forest
The Reds started the second half strongly with Bree again working room down the right to cross for Winnall, who failed to generate any power into his header, and Stojkovic calmly gathered.
Winnall again came close with a header from another excellent Marley Watkins delivery, but the effort drifted just wide of the target.
Another move started by Bree allowed Josh Scowen to charge down the middle of the park nine minutes into the second half. He combined with Hourihane before sending a rasping drive just over the crossbar.
Forest extended their advantage just past the hour mark when Michael Mancienne ran down the right and crossed for Osborn to glance home past Adam Davies.
Barnsley’s task went from bad to worse four minutes later as Watkins was shown a straight red card for an incident involving Forest midfielder Thomas Lam.
Lam could have extended Forest’s lead 13 minutes from time with a low effort from outside the area but Davies stood firm to deny him.
Lansbury completed his treble eight minutes from time after substitute Matty Cash was brought down by Scowen and the midfielder calmly rolled the ball past Davies.
Winnall almost pulled a goal back in stoppage time with a header from close range, but a reaction save from Stojkovic prevented the striker from adding his second.
Attendance: 13,180 (1,165 away)
Reds: Davies (GK), Bree (Janko, 74’ ), Jackson, Roberts, Yiadom, Watkins, Hourihane, Scowen, Hammill, Winnall (Williams, 88’ ), Armstrong (Bradshaw, 64’ ).
Subs: Townsend (GK), MacDonald, Morsy, Kent.
Nottingham Forest: Stojkovic (GK), Mancienne (Vaughan, 86’ ), Mills, Worrall, Perquis, Fox (Cash, 79’ ), Lansbury, Kasami, Lam, Vellios (Bendtner, 71’ ), Osborn.
Subs: Henderson (GK), Carayol, Lica, Grant.
