The hot-headed midfielder was sent off for elbowing City's Carlos Tevez, and he was charged with violent conduct for then kicking Sergio Aguero and trying to head-butt Vincent Kompany before being escorted off the pitch by his teammates.
Barton received an automatic four-match ban because the foul on Tevez earned him a second red card of the season.
The FA regulatory panel then gave him four-match suspensions for each of his violent actions after the dismissal. City won the game 3-2 after a last-minute comeback to clinch the league title, while QPR narrowly avoided relegation.
Barton was also fined 75,000 pounds ($118,000).
"There are rules of conduct that should be adhered to, and such behaviour tarnishes the image of football in this country, particularly as this match was the pinnacle of the domestic season and watched by millions around the globe," the FA said in a statement.
Since joining QPR, Barton has spent the last year — primarily through Twitter — trying to convince the public that he is no longer the volatile person who was previously jailed for a street assault and accumulated a long list of fines and bans from the FA.
At his first club, Manchester City, Barton punched a teammate in the eye during training and pushed a lit cigar into a teenage teammate's eye at a Christmas party.
After that incident in December 2004, Barton had another row with a 15-year-old Everton fan in Bangkok and City fined him eight weeks wages. The following season, Barton dropped his shorts and exposed his backside to Everton fans and was fined for misconduct.
In 2007, Barton appeared to have straightened out his life and he even got a call-up to the England team, going on as a substitute in a 1-0 loss to Spain.
But the bad behaviour soon returned and he was arrested after a violent argument with a taxi driver. He was then suspended by City after punching teammate Ousmane Dabo during training, which later led to a suspended jail sentence and the FA suspending him to miss six games.
Barton transferred to Newcastle in 2008 but he was arrested in Liverpool after a street fight and eventually received a six-month jail sentence for assault and fighting.
Barton was allowed to leave Newcastle on a free transfer in August 2011 following his public criticism of the club.
Even before being banned on Wednesday by the FA, QPR had said it would launch a full investigation into Barton's conduct at City.
FA chairman David Bernstein earlier this month urged clubs to consider firing players for misconduct despite the potential financial hit.
"Players are well protected by their contracts and sometimes overly protected in my view," Bernstein told a parliamentary committee. "If a club feels that by breaking a contract it could be involved in millions of pounds of settlements, it's a big disincentive.
"But the whole question of the nature of the contract and when a breach has arisen is an interesting one, and I hope it will be tested in the future."
Rob Harris can be reached at www.twitter.com/RobHarrisSuggest a correction