Matt Smith scored his first goal for QPR in a resounding victory at St Andrews.
Conor Washington scored the second and late goals from substitutes Idrissa Sylla and Yeni Ngbakoto capped a brilliant win.
Emilio Nsue’s injury-time consolation reduced the deficit on an otherwise perfect day for Rangers, who emphatically ended a five-match winless run and eased their relegation fears.
They started brightly and were rewarded when Smith headed home Luke Freeman’s 19th-minute corner.
Washington scored two minutes into the second half, firing into the far corner from the left-hand side of the penalty area for his third goal in five matches.
With six minutes remaining, Sylla netted with a diving header from Pawel Wszolek’s cross – the striker’s seventh goal of the season.
And, soon after also coming on, Ngbakoto registered his first Championship goal with an extraordinary strike.
The French winger caught keeper Tomasz Kuszczak by surprise, thumping a 30-yard free-kick in off the crossbar before Nsue pulled one back after being set up by Che Adams.
Freeman, making his first start for the R’s, linked up well with fellow January signing Smith, while the visitors controlled the midfield and were solid at the back in a hugely impressive performance.
After Freeman’s early half-volley was pushed away by Kuszczak, Smith’s attempted follow-up was blocked.
At the other end, Nsue missed a great opportunity for the hosts when he headed wide from three yards out.
Ryan Shotton then cleared off the line to deny Smith after the Rangers target man pounced on Cheick Keita’s poor header and lifted the ball over Kuszczak.
But the Birmingham-born Smith made no mistake when Freeman served up the perfect delivery from the left – and he would have scored again from another Freeman corner had Kuszczak not saved his header.
Kuszczak then produced another save, this time to keep out Wszolek’s header after the Pole had been found by Ryan Manning’s cross.
Birmingham ended the first half strongly and went close to equalising when Jerome Sinclair’s shot deflected off Joel Lynch and struck the bar.
But QPR doubled their lead soon after the restart and Grant Hall almost made it three with a header from Manning’s cross which Kuszczak did well to tip over.
Nsue shot narrowly wide and Greg Stewart wasted a great chance for Birmingham when he headed wide from close range.
Any prospect of a Blues fightback was then extinguished by two Rangers goals in the space of four minutes.
QPR: Smithies, Furlong, Onuoha, Lynch, Bidwell, Wszolek (LuaLua 85), Hall, Manning, Freeman, Smith (Sylla 80), Washington (Ngbakoto 85).
Subs not used: Ingram, Mackie, Luongo, Perch.
This post was last modified on 19/02/2017