The striker, out injured for the majority of the season, netted twice and was instrumental in the third goal as the Owls cruised to victory.
These two teams were in the play-offs 12 months ago, but started the day in the bottom 10 of the Championship.
Manager Jos Luhukay named Atdhe Nuhiu and Lucas Joao on the bench after recovering from injuries.
That meant Forestieri and Jordan Rhodes started up front.
Daniel Pudil was recalled in defence and there was a rare league start for goalkeeper Cameron Dawson, with Joe Wildsmith on the bench.
Forestieri curled an effort wide, while Rhodes failed to find the target as the Owls enjoyed the bulk of the early possession.
Dawson escaped after dropping a cross at the feet of Jon Dadi Bodvarsson, as Frederico Venancio cleared away the danger.
And the Owls took the lead on 34 minutes. Centre-half Pudil produced an overlapping run down the left, and his cross was volleyed home by Forestieri.
The goal-scorer then turned provider. He refused to allow a ball to drift away for a corner, keeping play alive, and when the cross was drilled in George Boyd converted from close range.
Substitutes Nuhiu and Joao - on for the injured Jack Hunt and Rhodes - combined after Forestieri's cross, but Joao was unable to net from close range.
This was turning into Forestieri's afternoon, and the striker capped it off with a stunning goal. He refused to be beaten as he battled through several challenges, before drilling in a long-range strike.
Tyler Blackett was sent off for an off-the-ball incident to add to Reading's troubles, late in the game.