The visitors claimed a 2-1 victory with almost the last moment of the match when Yoann Barbet headed home a late corner.
Charlie Austin had equalised from the spot for QPR just before half-time after Bristol City had taken an early lead through Alex Scott's deflected shot, which left R's goalkeeper Seny Dieng completely helpless.
Dieng had to be razor-sharp to keep out a back-heeled effort from Antoine Semenyo at his near post soon after as the Robins pushed for a second, and Semenyo missed another chance when he failed to connect cleanly with another dangerous ball into the box from Callum O'Dowda.
Matty James was the next Bristol City player to test Dieng, his shot into the turf looping up before the goalkeeper was able to grab it cleanly.
This all happened inside the first 15 minutes, and there were barely 20 minutes on the clock when Scott had appeals for a penalty waved away after he was bundled over inside the QPR box by Jimmy Dunne.
That decision stung all the more when moments before the break, the visitors were awarded a spot-kick after Luke Amos was put to ground inside the Bristol City box under a clumsy challenge from Cameron Pring. Austin made no mistake from the spot, and the sides went in level at the interval.
QPR appeared much brighter throughout the second half and was handed a further boost when Andy King was sent off after receiving a second yellow card on 56 minutes.
The numerical advantage had the Robins at full stretch for the remainder of the match as the visitors continued to pepper their goal, and the pressure eventually told in the dying moments when Barbet rose highest to glance home Stefan Johansen's corner, claiming all three points in the process.