Oscar's first half hat-trick downed the franchise Don's as Chelsea went into overdrive to blow away their Championship opponents 5-1 to breeze through to the fifth round of the FA Cup at Stadium MK
But plucky MK Dons had their moment in the sun when they equalised Oscar's opener.
But that was as good as it got for the home side, in a match that was far too open for either side's good, but which Chelsea capitalised on.
A penalty form Eden hazard and a neat strike from substitute Bertrand Traore sealed an emphatic win.
Chelsea should have taken the lead on three minutes when the Blues carved the Dons apart. On the right, Oscar slide the ball into the path of unmarked Diego Costa, but the Brazil-born Spain striker's first-time shot was brilliantly saved by David Martin.
Next up was Oscar, who half-heartedly tried to side-foot the ball home from eight yards out.
But his effort went wide of the home side's goal.
But on the counter-attack, MK Don's proved they could cause damage to the Premier League champions. A long run by Rob Hall was cynically halted by the outstretched leg of John Terry.
On 16 minutes the visitors took a deserved lead. Costa anticipated Kyle McFadzean's limp back pass and raced into the Don's penalty area.
In-running Oscar, supporting the striker, had the simplest of task to slide the ball home past Martin.
Seconds later er and Ruben Loftus-Cheek arrowed a blistering left-footer, on target. This time Martin was well placed to snaffle the effort.
Incredibly, while being outplayed, the home side looked dangerous on the scant times they got close to the Chelsea penalty area. And on 21 minutes they equalised through the right boot of Darren Potter, who's shot took a wicked deflection off Nemanja Matic and looped over hapless Thibaut Courtois.
Quite how Eden Hazard failed to put the Blues back in front is anybody's guess as he raced through on goal on 25 minutes. His effort grazed Martin and the ball bounced off his right past and back into his arms. A minute later and the Don's were exposed again, this time, Costa failed to get an outstretched leg to poke the ball home.
But class will out, and the Blues retook the lead on 32 minutes. Considered build-up play saw Loftus-Cheek tap the ball onto Oscar, who had got clear of the Don's' back four. He hit a first-time shot across the body of Martin and the ball nestled into the far corner of the net.
Just before the break, the tie was effectively over as Oscar notched up his first Chelsea hat-trick by smashing home a rasped of a shot from the edge of the penalty area, giving Martin no chance.
The second half started as the first ended with total dominance by the Blues. And within nine minutes goal number four duly arrived. This time from the right boot of Eden Hazard from the penalty spot after he was clipped in the area.
This signalled the first change by Chelsea boss Guus Hiddink, resting Costa and bringing on Bertrand Traore.
The Bukino Faso hit man took a couple of minutes to notch Chelsea's number five, when he whacked the ball past Martin after excellent service-up play by Hazard.
Willian and Pedro then entered the fray as Hiddink replaced Hazard and Oscar, presumably resting them for the midweek trip to Watford in the Premier League.
It was then just a case of militias, which the Blues did easily.
Teams Chelsea
Courtois, Ivanovic, Fabregas, Baba, Oscar, Hazard, Costa, Matic, Cahill, Terry, Loftus-Cheek
Subs, Begovic, Mikel, Traore, Pedro, Willian, Azpilicueta
MK Dons
Martin, McFadzean, Lewington, Walsh,Spence, Potter, Carruthers, Forste-Caskey, Murphy, Hall, Bowditch
Referee Jonathan Moss