MK Dons rallied from going a goal behind to eventually hammer Colchester.
Matt Heath gave the U's the lead when he headed home Lloyd James's cross before Charlie MacDonald levelled from close in, from Daniel Powell's centre.
Tom Flanagan fired in from Stephen Gleeson's corner to put the Dons ahead before MacDonald notched his brace from Mark Beevers' cut-back.
Gleeson added to the Dons' lead with a fine long-range effort before Jabo Ibehre sealed victory with a tap-in.
VIEW FROM THE DRESSING ROOM
Colchester manager John Ward told BBC Essex:
"At 2-1, coming out in the second period, we stepped our game up and had an opportunity or two to get that back and you would have seen the opposite happen.
"We did drop our heads a little bit, or just lose our spirit at 3-1 down, I understand that but I don't like it.
"We've disappointed them [the fans] today, I don't think we've let them down, I think we've disappointed them."
MK Dons manager Karl Robinson told BBC Three Counties Radio:
"I thought for 35 minutes that they were sensational the way they moved the ball and passed the ball. But strangely, their goal game from horrific defending from a corner and was one that I'm furious with.
"I went really mad at half-time, but they were also arguing with each other. There were a few home truths and I laid into them. In the second half, I thought we were a touch of class.
"We looked like a top quality team. Clinical, precise passing, defended really well. I thought we had all the components necessary in a good team."