Damion Stewart's header had given Rangers - watched by billionaire owners Flavio Briatore and Bernie Ecclestone - a deserved first-half lead, but Clint Hill and Clinton Morrison struck just after the hour to continue Palace's good run under Neil Warnock - who was sent-off at the death.
The two sides met only just over three weeks ago, with Morrison's late header salvaging an undeserved draw for Palace, but it marked the start of a turnaround for Warnock's team that has seen them go six matches unbeaten while, after a promising start, Luigi De Canio's QPR reign has stuttered, with his side winless in five.
And the gap in confidence was apparent from the off as Morrison tested Lee Camp within the first 15 seconds.
But against the run of play it was the hosts who took the lead after only nine minutes, Stewart rising highest to power home Akos Buzsaky's corner for his second of the season.
QPR were playing with a swagger that has been noticeably absent at Loftus Road this season and Palace keeper Julian Speroni was forced into three saves before the interval.
But it was Ben Watson's set-piece delivery that was to prove the difference between the sides, on-loan left-back Clint Hill reaching his free-kick after 64 minutes to flick the ball home from inside the six-yard box.
And suddenly the game was turned on its head as Morrison made it five goals in six games with a true poacher's effort, nodding home from less than a yard after Mark Hudson had headed Watson's corner against the bar.
Palace held out with ease against a QPR side clearly lacking in belief, although Warnock was sent to the stands in stoppage time for complaining about referee Alan Wiley's failure to send Camp off for timewasting after the keeper was caught with the ball well outside his area.