Second-half goals from Emmanuel Latte Lath and Marcus Forss gave Middlesbrough a 2-0 victory at Loftus Road and ended QPR's recent resurgence.
Latte Lath broke the deadlock on 64 minutes as Rangers were unable to clear a free-kick and Matt Clarke nudged the ball towards the Ivorian striker, who sent a right-footed volley past goalkeeper 12 Asmir Begovic and into the corner of the net.
Forss then doubled the lead 12 minutes later following a counter-attack after Rangers' Chris Willock appeared to have been fouled near the edge of the Boro penalty area.
Jonny Howson played the ball to the right to Luke Ayling, who crossed for Forss to head home at the far post.
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The defeat means QPR, who were unbeaten in their previous four matches, sit just one point above the relegation zone.
They were on the front foot for most of the first half and went close to scoring an early goal when Steve Cook's header from Lucas Andersen's right-wing corner struck Howson and went over.
The in-form Sam Field headed over from another Andersen corner and Ilias Chair fired wide as the hosts continued the threaten.
Boro goalkeeper Seny Dieng, playing against his former club, then pushed away a strike from Willock after some neat build-up play by Rangers.
Dieng was also able to keep out an audacious attempt by Chair to catch him off his line.
At the other end, Riley McGree blasted a shot wide of the target, but Boro offered very little before the interval.
They were better after the restart - prompting QPR boss Marti Cifuentes to make a triple substitution 10 minutes into the second half, sending on forwards Lyndon Dykes and Paul Smyth along with on-loan Newcastle midfielder Issac Hayden.
Playmaker Chair was one of those to make way and the home side struggled to create clear-cut chances after his withdrawal.
The changes initially had some effect, with Rangers showing more urgency and Dieng surviving another attempt to embarrass him - this time when Jimmy Dunne's lob from the right-hand side landed on the top of the net.
But it was Michael Carrick's Boro who seized the initiative and Rangers, who had started so brightly, faded badly and never looked like recovering after going behind.
The managers
QPR's Marti Cifuentes:
"Trust me, I don't need a defeat to have a reality check. It's a really difficult situation.
"I'm convinced that we're going to manage to reach the target, but if anyone thought it was easy they were making a big mistake.
"I'm not a magician. I'm here to help. But to expect we're going to win every game is delusional. It's going to be tough.
"We have a sad feeling because it's true that we had big expectations about this game and we didn't perform - not even close to the last game.
"We had a very demanding game on Wednesday, emotionally and physically, and Middlesbrough played 60 minutes against 10 men against Norwich, so perhaps that's one of the reasons they looked more energetic in the second half.
"It's very demanding when you have three games in just a few days and especially when you have Leicester away and West Brom, which were very demanding."
Middlesbrough's Michael Carrick:
"I keep saying about the spirit of the boys. It's easy when you're winning to say that, but when you have a tough spell - and we've had a couple of tough spells - you see people's characters and their real personalities.
"The boys have been incredible in terms of sticking together and finding a way through it.
"It's two big results for us. There's no getting away from that. The timing of the two results has been good and we've got two games coming up before the international break that we need to make the most of.
"It wasn't the prettiest game but what mattered most was the spirit and willingness to work for each other.
"I'm delighted. To find a way to grind out a win was pleasing. The boys did what they needed to do to get the win.
"It was a case of having the belief and backing themselves to go and win the game."