Dale Jennings opened his Reds account with a fine strike that was worthy of winning any match and, thankfully, his goal - along with a strong, determined performance - secured the points against Forest.
Jim O'Brien fired in a warning shot with just over a minute played but his effort went wide of the near post.
Winger Dale Jennings forced Darlow into a top-drawer save as he let fly from 25 yards. His attempt seemed to be dipping into the top corner but Darlow turned it onto the roof of the net with a good, strong hand.
Mackie should have scored for the visitors with a free header on 25 minutes but he planted his attempt wide from eight yards.
On 33 minutes Mellis worked wonders to drag the ball into the area but his cross was cleared after trying to find O'Grady.
Abdoun responded for Forest with a shot that cannoned off the foot of Steele's post after Mackie had laid the ball across to his team-mate 20 yards out.
Dale Jennings went one better on 51 minutes than his first half attempt as he let fly from 22 yards to find Darlow's bottom corner. It was just what the Reds, and Dale Jennings, were desperate for.
Forest responded by making a change with Darius Henderson replacing Jamie Mackie on 53 minutes.
The visitors were failing to trouble Steele in the Barnsley goal and made another change as Matt Derbyshire replaced Simon Cox on 65 minutes.
Steele made a routine catch from Paterson's tame header before Halford was replaced by Moussi for Forest's final change on 75 minutes.
Barnsley made their first change as Martin Woods made way for Emmanuel Frimpong with just less than 14 minutes to play.
The visitors were piling forward and putting the Reds under pressure but Barnsley were standing strong and battling hard to block every shot and cross possible as the clock ticked down.
The Oakwell faithful were in sensational voice in support of their team who were hanging on against the visitors' pressure.
A minimum of five minutes was added for stoppages and the tension was unbearable.
A corner in the fourth minute of stoppage time was hurled into the box but, thankfully, a shot was straight at Steele.
Liam Lawrence replaced Jim O'Brien in the dying seconds as it seemed the Reds had done enough.
Reds: Steele, Kennedy, Cranie (c), Ramage, Hunt, Dawson, Mellis, Woods (Frimpong 76), O'Brien (Lawrence 90), Jennings, O'Grady.
Subs: Turner, Frimpong, Cywka, McCourt, Proschwitz, Nyatanga.
Forest: Darlow, Halford (Moussi 75), Lascelles, Gomis, Fox, Jara (c), Abdoun, Majewski, Mackie (Henderson 53), Paterson, Cox (Derbyshire 65)
Subs: De Vries, Harding, Collins, Greening.
Referee: Keith Stroud
Man of the match sponsored by Napoleon's: Dale Jennings