QPR were punished for their shoddy mistakes in an all-too familiar defeat at the City Ground.
Alex Mighten, Lewis Grabban and James Garner scored for Nottingham Forest, where Rangers have won just once in the club’s history.
Lyndon Dykes scored a consolation goal for Rangers in the final seconds – a header from Albert Adomah’s cross.
They went behind following an error by Yoann Barbet a minute before half-time.
Barbet attempted to shepherd the ball out of play near the right-hand byline but was robbed by Sammy Ameobi, who teed up Mighten to score from close range.
It came after the visitors had missed a couple of very decent chances, with Stefan Johansen steering a shot wide and Charlie Austin lifting the ball over the bar after being found by Barbet’s left-wing cross.
Hopes of a second-half comeback were crushed by Grabban’s thumping 25-yard strike just after the hour mark.
Again it came after QPR had given the ball away. This time Dykes, just on as a substitute, was the guilty party.
And worse followed for Rangers when keeper Seny Dieng was caught out by Garner, who whipped a left-wing free-kick over him and into the far corner of the net.
QPR: Dieng; Dickie, Field (Bettache 80), Barbet; Kakay, Ball (Dykes 60), Johansen, Wallace; Chair, Willock (Adomah 68), Austin (Kelman 80).
Subs not used: Lumley, Hamalainen, Bonne, Thomas.