The 63-year-old was dismissed on Sunday night with Rangers 17th in the Premier League table.
Coaches Mick Jones and Keith Curle have also departed the Loftus Road club.
"Gutted to hear about the manager losing his job. We have to stick together as a club at times like these and believe in those above," Barton tweeted.
"I'd like to thank Neil, Keith and Mick personally for all they did whilst I was here and wish them all the best in the future."
Warnock signed Barton over the summer from Newcastle United.