Royals boss Alan Pardew used the game to give a number of his squad players a run-out, but they showed that they can do a job when called upon.
Tony Rougier marked making a rare start for Reading with the opening goal of the game after 27 minutes.
Darius Henderson doubled the visitors' lead after 70 minutes to put them in firm control.
Substitute Jamie Cureton wrapped up the win with the third goal deep into injury time.
The win secures fourth place for Reading and home advantage in their second play-off game but they are just one point behind third-placed Sheffield United.
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