The London club have now failed to win in all of their 31 visits to Forest, while Billy Davies' side had not won any of their previous five outings on the banks of the River Trent as their promotion challenge stuttered.
But a first-half header from Greg Halford and a controversial late second from Andy Reid secured a 2-0 win which lifted them back into the top six as Harry Redknapp's QPR suffered a second consecutive defeat.
Forest had Simon Cox ruled out with a virus prior to kick-off, which left Davies with a shortage of options up front.
Redknapp had a similar headache with Charlie Austin, the Hoops' leading scorer, sidelined with a hamstring problem.
Halford, Forest's most versatile performer, was pushed forward from his recent right-back role to instead play as a lone striker and the 6ft 3in player gave the visiting defence a few problems right from the off.
It needed a fine save from Robert Green to deny Halford what would have been a good goal, with the England goalkeeper saving bravely at his feet after the forward had skipped through the Rangers defence and through on goal.
Halford did fluff his lines when given a second opportunity, shooting wildly over the bar, but he made no mistake when given a third opportunity, powering home a header from close range after Djamel Abdoun had mesmerised the Hoops' defence with a twisting run and cross.
Benoit Assou-Ekotto had forced a solid save from Karl Darlow with a well-struck drive before the goal and Niko Kranjcar almost scored shortly after Forest had taken the lead, with his delightful curling effort flying just the wrong side of the post from 20 yards.
QPR responded by bringing on Andy Johnson and Junior Hoilett during the interval and they looked livelier for it, with Tom Carroll's dipping shot forcing a fine save from Darlow, who steered it over the bar.
Although Halford had another looping header narrowly clear the bar as he connected with Reid's cross and then missed a rather better opportunity, when Mackie picked him out unmarked in the centre only for Halford to prod the ball right at a relieved Green.
Clint Hill had to clear off the line when Green failed to properly deal with a high ball into the box, with Jack Hobbs sending a low shot fizzing towards the bottom corner.
Jenas also saw a spectacular drive deflected over and Richard Dunne's header was saved at the other end.
But then came the game's controversial moment, with Abdoun firing the ball through the centre, which Halford attempted to flick. The striker made no contact and the ball ran through for Reid, with the assistant referee flagging immediately for offside.
Referee Keith Stroud allowed play to continue and Reid calmly slotted the ball beyond Green to put the game beyond Rangers' reach in the 80th minute.