Dominik Frieser put the Tykes in front after 14 minutes and Cauley Woodrow doubled the visitors lead just before the half-hour mark. Ilias Chair pulled one back for the hosts until Charlie Austin levelled in the first minute of second-half stoppage time.
Story of the match
Barnsley had the better of the early play as Frieser threaded the ball through for Clark Odour whose shot took a deflection and went out for a goal-kick. Three minutes after that, the Tykes were in front.
QPR were caught playing out at the back, with a long ball sent towards Frieser, who had already gotten past his marker. He took a neat touch and sent a controlled effort skidding past goalkeeper Seny Dieng.
The visitors continued to attack and Liam Kitching sent a header just wide. Woodrow then sent one that trickled just past the left post and he would make the Barnsley pressure pay off.
Callum Styles' corner from the right is batted away by Dieng, but the visitors retained possession. Josh Benson and Styles exchanged passes, with the latter ghosting into the box to square for Woodrow, who is on hand to tap home and make it 2-0.
Woodrow then nearly had his brace on 31 minutes after a neat one-touch build-up, but Dieng reacted quickly to palm his effort behind. Into the second half, Romal Palmer and Yoann Barbet put more pressure on the QPR goal.
The hosts had their best chance of the match in the 57th minute as Jimmy Dunne rose to meet Chair's corner at the far post. He got above his marker but nodded just wide of the upright.
With the Hoops now growing into the game, Chair fed Austin, but he swiped his shot wide. The two combined again on 71 minutes with Austin flicking on Chair's delivery only to see Brad Collins denying him with a brilliant reaction save.
Chair then pulled one back for QPR, drifting in from the left after beating the offside trap, gliding past defender Toby Sibbick and rifling a shot past Collins and into the back of the net from a tight angle.
Barnsley nearly restored their two-goal lead as a ball was launched over the top, finding the run of Woodrow. He was able to round Dieng, but from a tight angle, he can only fire over the bar.
In stoppage time, the Hoops equalized. An overlapping run from Barbet found him receiving the ball from Chair before finding Austin in the box, who finished to make it 2-2.
The Tykes had a chance to win it as Sibbick broke out, charging all the way into the QPR box. A square pass to Devante Cole would have set him up for a glorious chance to score, but he was unable to find him and the game ended as it began with the teams level.
Man of the match: Charlie Austin
He does what he does: score goals and score them at crucial times. Always a threat when he's on the pitch, his interplay with Chair was fantastic and the goal was nothing more than he deserved.