Between them the sides are the joint top-scorers in the League but it took Scunthorpe midfielder Grant McCann to unlock the game.
Fouled 35 yards out when Craig Disley bundled into him from behind, McCann took the kick himself. A low angled shot clipped a defender and left keeper Steve Phillips wrong-footed.
For most of the first half the game had been upstaged by a fireworks spectacular from just behind the main stand but there were more in the home dressing room.
Coach Paul Trollope, who had received the divisional award as manager of the month before the start, had been less than happy with the quality of his side's tackling.
His centre-back, Steve Elliott, had been pressed into service after missing seven games through injury and acquitted himself well.
He gave away an early free-kick by toppling Sam Togwell but fell back in time to clear Togwell's well-directed kick off the line.
David Mirfin made a similar clearance to save Scunthorpe after Jeff Hughes had lobbed keeper Joe Murphy.
Both sides found the woodwork, Phillips turning a Martyn Woolford drive onto his left post and Rickie Lambert planting a 40-yard free-kick on the post behind Murphy's right shoulder.
After a quiet first half, Lambert was decisively closer 11 minutes into the second period when he dipped to head his 16th goal of the season from a cross by Disley.
Scunthorpe though were soon back in front, Gary Hooper drawing Phillips from his line to set up a tap-in for centre-back Izzy Iriekpen who had gone up for yet another free-kick.
It was his fourth goal of the season, putting the former Swansea City player ahead of McCann in the team's scoring charts and sending the Iron back up north with smiles on their faces.