With Plymouth Argyle sharing the spoils at Bristol Rovers, goals from Collins, O'Toole and McDonald sent Northampton to the top of League Two, Morecambe managing a consolation through Mullin.
4,652 watched the action at Sixfields, a slightly disappointing figure given the number who travelled to MK Dons in midweek.
Those in attendance saw another assured performance from Chris Wilder's who now have an 11-point cushion over Bristol Rovers in 4th.
More to come on Cobblers Mad.