Reading consolidated their Championship play-off place and hurt Scunthorpe's hopes of staying up in the process with a seventh successive victory.
Fresh from a 4-1 win over QPR, the Iron started impressively as Joe Garner and Chris Dagnall fired wide and then Alex McCarthy saved from Mark Duffy.
Reading improved after the break and went ahead when Shane Long swept in Jimmy Kebe's cross from the right.
Ian Harte's penalty wrapped it up after Michael Nelson fouled Long in the box.
The victory leaves Reading, fifth in the division, only three points away from an automatic promotion place after a superb run under Brian McDermott.
The future looks a little less assured for Scunthorpe, who are six points adrift of Crystal Palace in 21st with only five games remaining to secure survival.
Yet it could all have been so different as the hosts, buoyed by beating QPR and inspired by the impressive Garner in the opening stages, laid siege to the Royals' goal.
Garner and Dagnall might both have done better with their efforts wide and Garner saw another shot deflected behind for a corner.
Ramon Nunez also should have done better with his off-target strike from 10 yards.
Long made Scunthorpe pay with his 26th goal of the campaign after Kebe had come to life and when Nelson fouled Long and Harte slotted in, the game was over.
Dagnall and Nunez went close from distance for Scunthorpe, but Reading held on comfortably for the three points.