An early Armand Traore own goal and a superb finish from Ryan Lowe set the visitors on their way before Ryan Harley and Darren Potter heaped embarrassment on Harry Redknapp's sideLeague One side MK Dons shocked Premier League strugglers QPR with an amazing 4-2 win at Loftus Road to progress to the fifth round of the FA Cup.
Armand Traore put the ball into his own net after just four minutes following a Dean Lewington shot after a corner, and Ryan Lowe netted a brilliant volley after 40 minutes to put the visitors in dreamland.
Lowe then broke the offside trap to set up substitute Ryan Harley to hammer home from six yards before Darren Potter curled in a delightful effort to embarrass Harry Redknapp's men, despite two late consolation goals.
QPR started with vigour by winning a corner after just 10 seconds, and thought they had gone ahead within a minute, but DJ Campbell's volley was ruled out for a push beforehand.
The visitors were ahead just moments later though, with Traore flicking Lewington's shot into his own net after Shaun Williams put a low cross in from a Dons corner.
The visitors were confident in the early stages, with Ryan Lowe driving a strong effort from 25 yards straight at Green.
However, the early goal didn't unsettle the hosts unduly as they tried to get forward at every opportunity, with Park stinging David Martin's hands from the edge of the area.
While Redknapp's men poured forward, Dean Bowditch reminded them of Dons' attacking threat as he stole onto the ball on the half hour and struck a 25-yard effort wide of the post.
David Martin showed great judgement on 33 minutes to rush out and deny Jamie Mackie with the striker through on goal, blocking the forward's sliding finish away bravely with his body.
It seemed as though the hosts would be level soon enough with the pressure they were exerting, but the League One side shocked Loftus Road once more after 40 minutes.
A long ball through saw striker Lowe clean in on goal, and he showed superb technique and temperament to volley in on the bounce from 16 yards into the bottom right-hand corner of Green's net.
The half-time whistle brought with it a chorus of boos from the hosts' fans, who were desperate to see some quality on the ball after their side saw so much possession in the first 45 minutes.
Any half-time words of inspiration from Redknapp appeared to fall on deaf ears though, as Lowe broke the offside trap and pulled back for substitute Harley to put his side three up and send the 3155 visiting fans into further ecstasy.
Potter then curled in a lovely effort from inside the area after calamitous defending from the hosts, leaving the home crowd seething in fury while the travelling fans went delirious.
The shell-shocked hosts failed to mount a comeback, and although Jay Bothroyd and Fabio netted late consolations, it was a desperately disappointing day for Redknapp's side.