The 31-year-old struck late in the game to seal a scrappy, but vital, three points for the Magpies, who inflicted a first defeat on the Hoops under Harry Redknapp
Substitute Shola Ameobi curled a fine effort past Rob Green in the 81st minute to settle a scrappy game, played in torrential rain at St James' Park.
Alan Pardew kept faith with his starting XI that had gone down 3-1 to Manchester City the previous week, but Harry Redknapp made three alterations to the side that picked up a first league win of the season against Fulham: Fabio and Anton Ferdinand came into the defense, while Esteban Granero replaced Shaun Wright-Phillips in midfield.
In sodden conditions at St James' Park, both sides failed to create chances in a poor first half.
Adel Taarabt went closest for the visitors, latching onto Granero's clever scoop pass, but firing a shot from a tight angle straight at Tim Krul.
The hosts got themselves into several good positions down the left but were routinely let down by atrocious crossing from Jonas Gutierrez.
Papiss Cisse should have made more of a one-on-one chance, but his halfhearted effort, under pressure from Clint Hill, bobbled wide and Davide Santon unleashed a shot that flew high and wide.
The teams went in at the break deservedly goalless to rumblings of discontent from the home support.
The rumblings became full-on boos early in the second half as Papiss Cisse was hooked shortly after heading over the bar, the Senegalese striker, who has featured on the right wing recently, was visibly upset at the decision and refused to shake Alan Pardew's hand as he came off.
Harry Redknapp also made changes to his side, bringing off the quiet Esteban Granero and the frustrated Djibril Cisse in place of Shaun Wright-Phillips and Junior Hoilett.
The hosts almost took a fortuitous lead just after the hour mark as Vurnon Anita's corner almost crept in at the near post, but Green recovered well to scramble it away.
Ameobi then had a gilt-edged chance to score on 66 minutes, latching on to Vurnon Anita's cross eight yards out, but only getting a feather touch on the ball, and seeing it drift harmlessly wide.
The Magpies' tails were up and substitute Gabriel Obertan skipped down the left flank before cutting back onto his right foot and crossing for Demba Ba, who muffed his header, giving Green an easy save.
Newcastle finally snatched the lead with 10 minutes remaining, after some one-touch passing on the right, Ameobi was found in the box, before cutting inside and curling an unstoppable finish past Green.
The lead could have been doubled soon after as QPR committed men forward for a corner, but it broke down, giving Obertan and Sylvain Marveaux a chance to break. The latter carried the ball through the Hoops' half before firing a low shot that Green did well to save.
Marveaux also flashed a free kick just wide, and the visitors failed to muster a late challenge as they remain rooted in the relegation mire.