THREE goals in ten first half minutes provided the foundations for Nottingham Forest's biggest win of the season so far – which lifted them back into the play-off places.
Greg Halford, Simon Cox and Chris Cohen all struck just before the interval, to put Sean O'Driscoll's side in control after former Red Marlon Harewood had initially put Barnsley ahead.
Sub Jermaine Jenas, whose future is uncertain with his loan move from Tottenham set to expire this weekend, made it 4-1 after the break, as Forest made it three wins from their last four matches and lifted themselves back into the top six.
Forest, already troubled by defensive injury problems, suffered an early scare when Harewood went in late on Danny Collins. But, after taking some time to recover, the skipper was able to continue.
Radi Majewski seemed to have cleanly won the ball when he slid in to deny Stephen Dawson on the edge of the box, but referee Kevin Friend awarded a free kick. Fortunately for the visitors, Harewood's resulting shot was wild and flew high over the bar.
A loose pass in the Barnsley defence gave Andy Reid possession – and the chance to surge into the box, but Ben Alnwick was well placed to save his shot after the Forest man had cut back onto his right foot.
Simon Cox delivered an outstanding ball into the box after turning neatly on the right side, but Billy Sharp just failed to connect with a header on the run.
Harewood had another half chance at the other end, but completely miss-hit his angled shot and saw it bobble harmlessly out of play in front of the travelling Forest fans.
A foul on Reid brought Forest a free kick 25 yards out, which Greg Halford smashed powerfully into the defensive wall and, from the resulting melee in the box, Radi Majewski saw a dipping shot drop just the wrong side of the post.
Forest were looking dangerous going forward and should have gone ahead when Reid picked out Sharp with an outstanding cross, but the striker nodded the ball inches the wrong side of the post, before holding his head in his hands.
But it was Harewood who was to break the deadlock in the 24th minute, after Jacob Mellis played him in with a perfectly weighted pass to break the offside trap. The striker kept his head – and his footing – to neatly round Lee Camp before prodding the ball into an empty net.
Two minutes later Brendan Moloney had to clear the ball off the line, after Stephen Dawson had flashed a cross-shot towards the far post.
Forest almost hit back in spectacular fashion as Majewski danced around two defenders down the left before striking a low shot that, after taking a slight deflection, almost beat Alnwick at the near post, with the keeper getting down quickly to make a good save.
Sharp might have scored when Cohen clipped the ball across the face of goal, but the striker failed to make contact – although he seemed to complain to referee Friend that he had been held back.
Forest did pull themselves level, through an unlikely source, in the 35th minute, as Halford pushed forward to good effect.
The defender found himself with room to shoot just inside the box and, while he did not seem to connect properly with the outside of his boot, his low effort took a deflection off Scott Wiseman that beat Alnwick and carried it into the net.
And, three minutes before half time, Forest edged themselves into the lead with a well crafted goal. Cohen surged quickly down the right on a quick break before crossing into the centre where Sharp's instant shot was saved by Alnwick – but the keeper could only parry the ball to the feet of Cox, who provided a composed finish.
There was time for more before the interval, as Forest stamped their authority on what had been a tightly contested first half with a spectacular third. Reid had caused chaos with a darting run down the left and, when his cross was cleared to the edge of the box, Cohen took full advantage, lashing a shot high into the corner of the net, beyond Alnwick, who got a hand to it, but could not keep it out.
The second half began with more positive play from Forest, playing in their blue away kit, with Cox sending an overhead kick looping over following a progressive passing move down the left.
Eight minutes into the second half, Barnsley made a double change as they looked to find a way back into the game, with Tom Kennedy and Kelvin Etuhu introduced in place of Matt Done and Tomasz Cywka – and then made a third change in the 56th minute, when Chris Dagnall repaced Dawson.
Kennedy forced a save, low to his left, from Camp, with a clever free kick bent towards the near post.
Forest's defensive woes took a blow when Halford collected a yellow card for a foul, earning him a suspension as it was his fifth booking of the campaign. With Sam Hutchinson, Daniel Ayala and Jamaal Lascelles injured, the arrival of Elliott Ward on loan from Norwich this week began to look more important.
The Reds were still pushing for a fourth goal, however, with Sharp forcing a corner and then, when Reid delivered, seeing a header pushed away by Alnwick. Cohen came close to adding another to his personal tally as he struck a left-foot shot that bounced awkwardly in front of the keeper, who did well to hold.
But substitute Jenas did make it 4-1, as Cox threaded a pass through the centre for the midfielder to chase. Jenas' pace took him clear and, as Alnwick raced off his line, he lifted a clever chipped finish over the keeper and in.
O'Driscoll chose to give Ward the chance to settle in to the back four by bringing him on for the final ten minutes, in place of Halford, whose place in the side he is almost certain to take against Millwall next weekend.
Barnsley: Alnwick, Stones, Foster, Wiseman, Golbourne, Dawson (Dagnall 56), Perkins, Done (Kennedy 53), Cywka (Etuhu 53), Harewood, Mellis. Subs: Steele, Hassell, McNulty, Rose.
Forest: Camp, Moloney, Halford (Ward 80), Collins, Harding, Gillett, Cohen, Majewski (Jenas 71), Reid (Coppinger 82), Cox, Sharp. Subs: Darlow, McGugan, Greening, Blackstock.
Referee: Kevin Friend.
Attendance: 10,186 (2,217 away)