West Brom opened the scoring in the first half though Chris Brunt, who struck from outside the area in the 29th minute. The visitors doubled their advantage early in the second half when Rob Green turned the ball into his net for an own goal in the 49th.
QPR pulled one back in the 68th as Djibril Cisse scored from close range but West Brom hung on for all three points and its first victory in the capital since a 3-2 win over Arsenal at the Emirates Stadium in 2010.
West Brom moved up to fifth in the standings with 33 points, behind Everton in fourth on goal difference. QPR drops to the foot of the table with 10 points, behind Reading on goal difference.