A comical own goal gifted the Baggies a two-goal lead that the hosts could only halve, thanks to Djibril Cisse's intelligent finish
A first-half strike from Chris Brunt and a Robert Green own goal gave the visitors a convincing lead - one that they would hold onto despite a Djibril Cisse goal that briefly inspired the home side.
The hosts began the game positively as Stephane Mbia curled a shot from 20 yards just wide of Ben Foster's post, but that turned out to be the only moment of danger either side posed in the early going.
West Brom had barely threatened Robert Green's goal, but the excellent Mulumbu, reinstated to the side following suspension, was afforded too much time in the hosts' half, allowing him to feed the ball into Chris Brunt. The Northern Irishman had ample space to steady himself and rifle a powerful low drive from 25 yards past Green to hand the visitors the lead.
West Brom carried the momentum into the second period and although Anton Ferdinand was fortunate to see his chested clearance rebound behind goal and not past Green, the Rs were not as fortunate moments later.
Armand Traore's skyward header from Brunt's corner caused consternation in the box, allowing Marc-Antoine Fortune the time to back into Green on the goal line. As the two players jostled, it was Green's touch as he tried to palm the ball over his bar that saw QPR fall 2-0 down. The hosts felt aggrieved but referee Chris Foy adjudged the tangle to be legal.
As QPR chased the game Harry Redknapp introduced Junior Hoilett and Samba Diakite and although Lukaku trundled through on goal only to be denied by Green once more, it injected new life into the Rs.
Mbia, who had been one of the hosts' better players, found room to slide a ball into Cisse. With the pace just right, the Frenchman did not need to break stride as he lifted his finish over the onrushing Foster to provide QPR with some hope.
Though QPR grew in confidence, the Baggies remained resolute, though they had to rely on a superb save from Foster in the dying stages to prevent Hill's header equalizing.
A seige on the West Brom goal yielded plenty of half-chances but by the final whistle the Midlands side survived, preserving its place in the Premier League's top six.