The Swans slumped to a fourth consecutive defeat as QPR claimed a crucial win in their battle against relegation.
After a 4-0 defeat here in the Championship last season, the Swans went down 3-0 on this occasion following goals from Joey Barton, Jamie Mackie and Akos Buzsaky.
This defeat left the Swans ten points clear of third-bottom Bolton - who had a game in hand - with five games to go.
The Swans make two changes from the starting XI that lost to Newcastle last time out.
Former QPR loanee Scott Sinclair and top scorer Danny Graham return to the starting XI with Nathan Dyer and Luke Moore dropping to the bench, while another former Rs winger Wayne Routledge retains his place out wide.
The hosts welcome back Joey Barton and Bobby Zamora to their starting line-up while Shaun Derry misses out through suspension.
QPR: Paddy Kenny, Samba Diakite, Clint Hill, Adel Tarrabt (Tommy Smith, 88), Jamie Mackie (Shaun Wright-Phillips, 78), Akos Buzsaky, Joey Barton (capt), Taye Taiwo, Anton Ferdinand, Nedum Onuoha, Bobby Zamora (Jay Bothroyd, 78).
Subs: Radek Cerny, Danny Gabbidon, DJ Campbell, Luke Young.
Swans: Michel Vorm, Angel Rangel, Steven Caulker, Ashley Williams (capt), Neil Taylor (Alan Tate, ht), Leon Britton (Luke Moore. 62), Joe Allen, Gylfi Sigurdsson, Wayne Routledge (Nathan Dyer, ht), Scott Sinclair, Danny Graham.
Subs: Gerhard Tremmel, Garry Monk, Mark Gower, Josh McEachran.
In a lively start, the Swans dominated possession but it was the hosts who went close in the opening few minutes with Akos Buzsaky trying his luck before Michel Vorm denied Jamie Mackie although the latter was ruled offside.
The Swans then went within inches of opening the scoring, Steven Caulker nudging Gylfi Sigurdsson's corner towards goal but Scott Sinclair failed to connect and Joey Barton cleared off his own line.
QPR replied with Bobby Zamora controlling a cross in the box and teeing up Mackie, but his weak effort bundled towards Vorm.
Sinclair then got ito the middle of things again, Danny Graham nodding down Caulker's ball to Sinclair in the box, but his shot on the turn 12 yards out was well blocked by Clint Hill, with Wayne Routledge firing over from the rebound.
Angel Rangel then fired straight at Paddy Kenny before, at the other end, Zamora shot over from eight yards after Vorm parried Adel Taarabt's corner.
And with one minute of added on time to come, QPR won a free-kick and Taarabt's delivery was nodded out by Rangel to Barton, who fired low into the corner.
Half-time: QPR 1 Swans 0
Brendan made a double change at the break with Alan Tate and Nathan Dyer replacing Neil Taylor and Routledge.
Caulker's mazy run upfield then set up Joe Allen. whose 25-yard effort was parried by Kenny before the hosts doubled their lead. Mackie, who appeared to be in an offside position, collected posession and turned off his right shoulder before his shot deflected off Rangel and beat Vorm.
Stunned by the goal, the Swans went close to cutting the deficit when Hill's attempted headed clearance from Sigurdsson's free-kick deflected off Graham and bounced just wide.
The Swans pushed again, Caulker's header back towards goal from another Sigurdsson delivery looked goalbound before Hill cleared over the crossbar.
Brendan then made his final change just after the hour with Luke Moore replacing Leon Britton. That saw Moore operate as the attacking member of the midfield trio with Sigurdsson and Allen behind.
But QPR, cruelly, added another just moments after a scramble at the other end. Following a quick counter, Akos Buzsaky let rip with a 25-yard thunderbolt which Vorm had no chance in keeping out.
The rest of the game saw the hosts on top with the Swans deflated, and victory for the Rs provided them with a massive lift in their battle against the drop.