Steve Coppell's Reading were beaten 3-0 at home by struggling Palace, with Andrew Johnson and Wayne Routledge scoring within six first-half minutes and Johnson adding a late third.
Symons himself sat out the game through suspension and watched his team get off to a positive start with the eventual goalscorers shooting just wide and Neil Shipperley heading Danny Butterfield's cross against the woodwork.
Then Aki Riihilahti beat one and played a clever reverse ball to Johnson who finished well for his 12th goal of the season.
The former Birmingham man played an integral part in the second goal too, bursting clear down the right wing and supplying the pass which left Routledge with a simple tap-in.
And Palace's dominance continued after the break. Shipperley's low drive was saved by Marcus Hahnemann, Tony Popovic headed over, Julian Gray's shot was just too high and Routledge was within inches of a second.
Apart from a rising cross-shot from Nicky Shorey, Reading threatened little until Scott Murray drew an excellent save from on-loan keeper Thomas Myhre in the final few minutes.
It could have set up a nervy finale but instead Johnson slid in his second and Iain Dowie inherits a team now 19th in Division One.
