QPR scored after only 47 seconds through Adel Taarabt then defended in depth to withstand a Barnsley onslaught and claim the three points. Rangers are now on the verge of promotion to the top flight, depending on the outcome of a Football Association charge regarding the ownership of Argentinean midfielder Alejandro Faurlin which could result in a points deduction.
Boss Neil Warnock said: "If you look at all the games where the team scores in the first minute, the other team will always come at you. That's when you have to hang in there.
"Tonight I thought we defended magnificently, and I think that started at the front.
"Barnsley had a good win on Saturday, they've got some good players and with the crowd being an extra man for them, that makes this such a great win for us.
"To bounce back from the defeat on Saturday - this league is so unpredictable.
"We could have won 5-0 on Saturday but we lost 4-1, it's that type of league.
"Adel (Taarabt) took his goal fantastically, he's the only player on the park that would have scored that.
"I had to take him off with all the tackles coming in. If they don't give a card for tackles like that, there's going to be some damage."
Barnsley chief Mark Robins remained philosophical despite the defeat.
Robins said: "Overall we got the ball into the box well but we just didn't have enough movement to put the ball into the net.
"When it did fall to Andy (Gray) in the first half, (Paddy) Kenny made a decent save.
"That's the only downside - the first 90 seconds we couldn't do anything about - apart from that I think we passed the ball well.
"We had most of the possession tonight and that's going to show in the stats.
"I was pleased with everything we did except sticking the ball in the back of the net.
"They're the league leaders and probably the champions and they made it difficult for us. It's a side that's led from the front all season."