Doubts over whether Barton has a future at Loftus Road were fuelled earlier on Thursday when his old number 17 shirt was given to summer signing Ryan Nelsen.
The midfielder must serve a 12-game ban to start the season after his red card and violent conduct in the final match of the last campaign against former club Manchester City.
It now appears the 29-year-old, who was also stripped of QPR's captaincy over the summer and had been training with League Two side Fleetwood Town, will spend the season in France, according to Sky Sports News.
Barton was linked with a loan move to Fleetwood but it is understood the Football League would block the former Newcastle and Manchester City man joining one of its clubs on loan while his ban remains in place.
A move to France will mark the first time the once-capped England international, formerly of City and Newcastle, has plied his trade at an overseas club.
Mbia, who can play at centre-back and in midfield, is poised to move the other way on a season-long loan.
The 26-year-old Cameroon international joined Marseille from Rennes in 2009 and made 15 Ligue 1 appearances last season.
On Thursday night, Barton teasingly wished his Twitter followers "Bonne nuit" - French for "good night".
