The Baggies had looked like a side who had taken just a point from their previous four games, but Gera popped up at the far post to prod home Nathan Ellington's cross after 84 minutes.
The unlucky Hoops saw Dean Kiely save a penalty from Paul Furlong on 66 minutes with the scores level at 1-1 after Furlong's run into the box had forced a clumsy challenge from Robert Koren.
Four minutes earlier a Dexter Blackstock header had cancelled out Kevin Phillips' 48th minute strike.
The best chance of a dreary first half fell to Furlong after 38 minutes. Gareth Ainsworth put an enticing cross into the box from the right and the rangy striker looked set to score before heading over.
The home fans screamed that Furlong had been pushed by Paul Robinson but to no avail.
West Brom then took the lead on 48 minutes. The away side broke through Jason Koumas, who slipped a pass to Phillips and the former Sunderland striker fired home his 16th goal of the season from ten yards.
QPR manager John Gregory sent on Blackstock after 62 minutes and the substitute took just a minute to bring the home side level by heading an Ainsworth cross into the bottom right-hand corner.
The home side should have gone ahead on 66 minutes when Furlong won a penalty after a clumsy challenge for Koren. He took the spot-kick himself but Kiely dived low to his right to save.
But Gera had the final say and was booked after over-celebrating in front of the jubilant away fans.