Manager Steve Clarke decided to hand a debut to new loan signing Nathaniel Chalobah who played in a midfield also consisting of regulars Oliver Norwood and Danny Williams.
The change didn't have much success in the first-half as Reading fell behind to a Kenwyne Jones header midway through the first 45.
The day got worse soon afterwards as regular right-back Chris Gunter hobbled off injured to be replaced by Stephen Kelly.
However the game had a happy ending for the more than 1500 travelling Royals who first saw Oliver Norwood fire home a free-kick on the hour mark before Hal Robson-Kanu flicked home at the near post from a Jordan Obita cross.
So Reading into the fifth round and with Premier League leaders Chelsea knocked out by Bradford, it's surely our cup to lose right?
Bucks Royal will be along will a full report and player ratings in the next 24 hours so check back in for that as well as all the latest news and analysis right here on The Tilehurst End.
In the meantime, catch the goals here.