A last-gasp goal from Gylfi Sigurdsson earned Reading another FA Cup upset as Burnley became the fall-guys at the Madejski Stadium.
The Royals had knocked Liverpool out at Anfield in the third round and added another top-flight scalp as the Clarets' miserable away form continued.
Burnley had looked set to earn a hard-earned replay as they repelled a late push from the Championship strugglers in search of a first clean sheet in 12 games.
But that and the prospect of a morale-boosting cup run under new boss Brian Laws was snatched away from them in the 87th minute when Sigurdsson pounced.
David Edgar had almost won it for the Clarets at the other end but Burnley could have few complaints on a day when they failed to find top gear and provided new boss Laws with plenty to ponder as he now looks forward to trying to mastermind a survival campaign.
Burnley had started with the welcome sight of Chris McCann's name on the teamsheet as the Irishman returned to frontline duty following four months out with a knee injury.
And his versatility came in handy for Laws as he was forced to slot in at left-back in place of the injured Stephen Jordan and the absent Christian Kalvenes.
With Steven Fletcher not risked after picking up an ankle injury last weekend at Old Trafford and on-loan striker David Nugent ineligible, Laws also saw his options reduced in attack where Steven Thompson was asked to play a lone hand.
The Scot was not 100 per cent after being unwell overnight but was at least armed with the happy memories of his last trip here when his stunning goal helped the Clarets secure their famous play-off semi-final victory.
Since then Reading have gone into seemingly terminal decline, losing two managers and slumping this season into the Championship relegation zone.
A wretched home record of just two league wins in 12 months has been behind their fall from grace but their shock cup win on Merseyside had offered some respite.
And the Royals were certainly not cowed against more Premier League opposition as they shaded a drab first half which lacked any of the magic traditonally attached to the competition.
Those supporters left watching a blank screen as the FA's scheduled webcast failed to fire missed nothing as Burnley failed to click going forward, despite the best efforts of Chris Eagles, and Reading enjoyed moments of promise without troubling Brian Jensen.
The Clarets' keeper watched a couple of speculative shots from Grzegorz Rasiak and Sigurdsson drfit either aimlessly wide or harmlessly into his chest, while at the other end Adam Federici was even more under-employed.
Laws responded at the break by sending on Martin Paterson in place of Thompson as the striker also ended his lengthy injury absence with the opportunity to get his first goal since his stunning strike here in the play-offs in May.
Paterson provided an injection of pace to the Clarets' front line but it was Reading who finally delivered the first real threat on goal as Simon Church collected a Rasiak flick to let fly with a shot which forced Jensen to save high to his right.
With the tie finally starting to come to life Burnley replied with a spell of more composed football, Wade Elliott teeing up Graham Alexander for a shot which skidded wide.
That was the trigger for Burnley's best spell of the game and with 58 minutes gone they almost went ahead.
Eagles and Tyrone Mears combined neatly on the right flank and when Eagles crossed to the near post Joey Gudjonsson flicked the ball goalwards but was denied by Federici's sharp save.
Gudjonsson was then involved in his own penalty area as he stopped the lively Jobi McAnuff in his tracks, sparking penalty appeals from the home side but no reaction from referee Andy D'Urso.
It looked a correct decision but the Clarets were fortunate not to go behind moments later when Sigurdsson headed wide a Ryan Bertrand cross from in front of goal.
That was a major let-off for Laws' men and they almost capitalised with a quarter of an hour to go. A rapid break ended with Kevin McDonald forcing Federici into a save low to his right and the big Australian followed it up with a stunning stop to keep out a David Edgar header from the corner that followed.
Paterson was unable to convert the rebound as he lifted his effort over the top and Reading then piled on the pressure in search of a late winner.
Jensen stood firm to repel headers from Matt Mills and Shane Long but the Royals booked their place in the last 16 three minutes from the end when Sigurdsson, whose equalising penalty at Anfield had set up their giant-killing in the previous round, grabbed the winner.
Running onto a pass from Andy Griffin, the Icelander rounded McDonald and steered a low shot past Jensen to gain a measure of revenge for last season's promotion heartache.
Reading: Federici, Mills, Gunnarsson (Kebe 74), McAnuff, Ingimarsson, Church (Long 64), Karacan, Rasiak (Thorvaldsson 84), Bertrand, Sigurdsson, Griffin. Substitutes: Cisse, Pearce, Howard, Hamer.
Burnley: Jensen, Mears, McCann, Duff, Edgar, Alexander, McDonald, Gudjonsson (Blake 85), Eagles, Thompson (Paterson ht), Elliott. Substitutues: Carlisle, Rodriguez, Guerrero, Easton, Penny.
Referee: Andy D'Urso.