The controversial midfielder was shown a red card at the Etihad Stadium for elbowing Carlos Tevez, and he then kicked Sergio Aguero before attempting to headbutt Vincent Kompany.
The FA announced Barton received an automatic four-game suspension, with the additional eight matches a consequence of the manner of his dismissal. He was also fined £75,000.
QPR chairman Tony Fernandes: "QPR will be making no comment in regard to the Joey Barton case. Internal investigation will begin in due course.
"There are experienced people who will come back to me and we'll review the whole situation.
"Joey has been an integral part of the club and has played his part.
"This is football, and I'm new to it. I don't profess to have all the answers."