Town went down to a second successive defeat as Reading found their goal touch at the Madejski Stadium.
The Royals hadn’t scored in their last seven home games but an Orlando Sa hat-trick and further goals from Nick Blackman and a rocket from Northern Ireland international Oliver Norwood inflicted a heaviest defeat in three years on Blues.
Freddie Sears had put Town level inside the first 10 minutes but Sa restored Reading’s advantage almost immediately and despite having chances, it was uphill for Blues from there.
Mick McCarthy made two changes from the side that went down to Brighton before the international break, with David McGoldrick and Christophe Berra returning to the starting line-up at the expense of Josh Emmanuel and Ainsley Maitland-Niles.
Reading started on the front foot, Berra clearing the danger twice in quick succession from crosses into the box and there was only seven minutes on the clock when the Royals went in front, Sa heading in from close range from an excellent Blackman cross.
Town took only three minutes to level though, Sears in the right spot to knock the ball over the line after Jonathan Bond had saved superbly from Ryan Fraser.
Blackman tested Dean Gerken at his nearpost after cutting inside from the right but the Town ‘keeper was beaten moments later when Sa found the bottom corner from the edge of the box.
Sears hooked the ball back into the box but Bond ended the danger as the game continued to flow from end to end, Jonas Knudsen then rifling a right foot effort just wide.
Sears showed a great touch to find space inside the Reading box but he couldn’t keep his shot down from Fraser’s excellent pass, then the Scotland U21 international blasted over from 25 yards.
Matej Vydra almost capitalised on a Reading break that saw the Royals outnumber Town five to two at one stage, Knudsen then doing well to shadow the run of Blackman as Gerken smothered the danger.
Luke Chambers blocked Stephen Quinn’s effort, Blackman’s chip going harmlessly wide of Gerken’s far post.
McGoldrick couldn’t get his header on target from Fraser’s corner as Town went into the break a goal down.
Brett Pitman smashed a right footer high and wide as Blues threatened to get back on level terms early in the second-half but it was the Royals who struck, Blackman finding the roof of the net from the angle on 49 minutes after in-decision in the Town defence.
Sears curled a shot over as Town looked for an immediate response, Vydra doing likewise for Royals.
Pitman thumped a header against the bar but Reading put the game out of sight with a fourth on 65 minutes, Blackman again the provider and Sa completing his hat-trick with a tap-in.
Blues changed it around with Daryl Murphy introduced for Pitman and Maitland-Niles for Fraser, the Arsenal loanee volleying wide at the far post.
Norwood scored the goal of the night three minutes from time with a 30 yard thunderbolt as Blues suffered a heaviest defeat since the 6-0 loss to Leicester in November 2012.