The hosts led through none other than Charlie Austin but goalkeeper Rob Green was sent off in the second half, conceding a penalty that the visitors converted.
Forest then went on to add more and Green was ultimately blamed for costing QPR the game.
The 35-year-old did, however, did take to Twitter to apologise to supporters after the game:
Second sending off in 550 games.Disappointed to be the catalyst of defeat and can only apologise.Hoping for 275 more games till the next one— Robert Green (@Robert1Green) September 12, 2015
And QPR fans certainly appreciated the apology. But Green still got plenty of stick from fans after his Nottingham Forest gaffe, with his kicking in particular being scrutinised.
Many are hoping the veteran goalkeeper's mistake doesn't end up costing QPR over a number of games (as he will now be suspended), with the R's no doubt keen to build on the momentum they had got going before the Forest defeat.
Here's how QPR fans responded to Green's performance against Nottingham Forest, then, including their reaction to his admirable apology. The west London side now drop to seventh - but it is early days and they are only six points off top...
Fair play to Rob Green for apologising. Silly split-second thing to do and I bet he knew it the second it happened. #qpr— Steve S (@RuislipR) September 12, 2015
I see rob green has apologised on Twitter.. A lot wouldn't have bothered #qpr— steve patrick (@spatpat56) September 12, 2015
Green's kicking was poor all game he laughed it off twice in the game. Someone should have got stuck into him. No leadership today #QPR— Nick (@nick_ranger73) September 12, 2015
Have to say, for a GK of Green's quality, being that poor on the ball is criminal. That wasn't a one off today. Just one that cost us. #QPR— S Michail (@smichail89) September 12, 2015
Just hope Green's mistake doesn't cost us in the long run. Bet players are devastated and I am sure a lot of heads have dropped. #QPR— Owen (@QPRFORLIFE) September 12, 2015