Ian Bradbury fired a hat-trick as Moulton Harrox hit Crowland Town for six.
Mathew Barnett, Billy King and substitute Andrew Law were also on target for the hosts in the Peterborough and District League Premier Division clash.
On Saturday Harrox face a trip to league leaders Oakham United who won at Pinchbeck United last weekend with a single first-half strike.
Harrox, meanwhile, will face Brumby at home in the Lincolnshire FA Junior Cup semi-final on February 14.
Tom Elderkin struck for Spalding Town in the first half but after the break they conceded three times as Brumby ran out 4-1 winners.
Other Premier Division action saw Deeping Rangers Reserves come from 2-0 down to win 5-3 at Peterborough ICA Sports – despite playing the second half with 10 men and missing a penalty.
Connor Pilbeam – who joined Rangers from Eye United last month – scored a hat-trick and Sam Thompson added a double.
Langtoft United slipped to a fifth successive defeat in league and cup as they went down to two early goals at Coates Athletic.
That run has included four matches against the Premier Division’s current top three – a tough sequence of fixtures that the Vikings are glad to put behind them.
Langtoft manager Phil Gadsby said: “It’s been a hard few weeks for us, with a run of fixtures I’m sure no-one would envy.
“That being said, we haven’t given a good enough account of ourselves. We’ve gifted teams goals and they really don’t need the extra help from us to put the ball in the net.
“On Saturday I thought the lads battled well and showed a desire to compete, but didn’t really pose much of a threat going forward.
“We pride ourselves on being an attacking team, so it’s disappointing to not be creating chances, but if the lads show the same fight that they did in the second half on Saturday then I’m sure we’ll turn the corner sooner rather than later.”
Saturday saw a second game for new signing Ben Salis and a debut for midfielder Nicky Butler.