The Iron extended their unbeaten run to eleven matches with an emphatic 4-1 victory at Walsall on Saturday, which puts United in 17th place.
An own goal from home defender James Chambers opened the scoring before on-loan striker Tom Hopper netted a goal on his Scunthorpe debut.Michael Cain pulled one back a few minutes into the second half, but a Paddy Madden penalty and a Neal Bishop goal secured the Iron’s biggest win of the season.
Scunthorpe are now only seven points off the League One play-offs and have games in hand over several of their rivals.
Elsewhere in League One, Bristol City moved back to the top of the table with Swindon Town not playing until Monday evening, when they travel to Coventry.
Goals from Joe Bryan, Matt Smith, Jay Emmanuel-Thomas and Derrick Williams sealed a 4-0 victory for City against Shaun Derry’s Notts County.
MK Dons missed the chance to move within a point of the top two, drawing 2-2 at Crawley Town, although they had to fight back from 2-0 down.
Izale McLeod’s brace had put the hosts in a commanding position, but Will Grigg gave the Dons hope 15 minutes from time before Delle Ali’s stoppage time goal snatched them a point.
Preston also failed to close the gap between themselves and the top two, falling to a 2-1 away defeat to fellow promotion hopefuls Sheffield United.
Marc McNulty and Jamal Campbell-Ryce put the Blades 2-0 up, with Josh Brownhill’s goal proving no more than a late consolation.
Ten-man Bradford lost for the first time in seven league matches as they fell to a 2-1 defeat at home to Rochdale, thanks to Calvin Andrew’s injury time winner.
They had played nearly 80 minutes with ten men after ‘keeper Jordan Pickford’s red card, but Jon Stead’s goal looked to have cancelled out Peter Vincenti’s equaliser, only for Dale to striker late on.
Crewe moved out of the bottom four after a 3-1 home win against Gillingham, who now drop below their opponents and into 21st.
Colchester are still in the bottom four despite picking up a 2-0 win at Peterborough. Freddie Sears and Elliott Hewitt scored for the Essex side.
There was an entertaining game at Boundary Park as Oldham and Doncaster played out an exciting 2-2 draw, with hosts two up at one point, only to end the match with ten men.
The Iron’s FA Cup opponents Chesterfield enjoyed a comfortable 3-0 victory over Port Vale at the weekend, while Barnsley beat ten-man Yeovil 2-0 and Fleetwood enjoyed a 1-0 success at Leyton Orient.
Next up for the Iron is the visit of high flying Bristol City, although Mark Robins’ side will go into the match hoping to extend their unbeaten run to 12 matches.