The Royals scored twice in the first 18 minutes and could have added more in the opening half hour, which they totally dominated.
They went ahead after just 12 minutes with one of the best goals scored at the Madejski Stadium this season.
Tricky winger Jimmy Kebe beat four Preston defenders as he cut in from the right wing before finishing his run with a clinical shot past Wayne Henderson in the Preston goal
Five minutes later, Reading added a second, this time from the left wing as Jobi McAnuff cut inside and sent his shot across the face of goal into the far corner of the net.
Preston's problems were compounded by an injury to Barry Nicholson, making his first appearance since he broke a leg against Darren Ferguson managed Peterborough in August.
Nicholson lasted just 13 minutes before limping off with what appeared to be an ankle injury.
The first threat to Reading keeper Adam Federici came 12 minutes before the break but Matt James hammered his effort into the ground to take out the sting and help Federici make the save.
Ross Wallace was desperately unlucky not to reduce the arrears midway through the second half.
A mistake by Andy Griffin allowed Wallace to run through on his own from the hallway line but, with only Federici to beat, he sent his shot thumping against the keeper's left-hand post.
He made up for it a minute later with a ferocious 30-yard free kick that rocketed past Federici for Preston's only goal.
Reading added their third 18 minutes from time after Shane Long made a dash through the Preston defence.
The ball ran to Kebe whose shot rebounded to the club's player of the season Gylfi Sigurdsson, who scored his 20th goal of the campaign.
Two minutes into injury time, Simon Church completed the scoring with a sensational long-range drive that gave Henderson no chance.