Barton, 29, had complained that the move had collapsed but took to Twitter on Wednesday to say he was on his way to Marseille to discuss terms with the Ligue 1 giants.
"Off to Marseille. It's on. Its off. It's back on again. I am still sceptical," the former Manchester City and Newcastle midfielder said on Twitter, accompanying his comments with a photo of himself on a flight before expressing his pleasure at how warm it was on arrival.
French journalists reported he spoke to them at Marseille airport, saying that OM was his preferred destination.
Reports have linked the Englishman with either a one-season loan deal or a swap involving Marseille's Stephane M'Bia.
Barton is expected to leave QPR after boss Mark Hughes decided to cut his losses on the controversial midfielder, who is sitting out a 12-match ban following his sending-off against Manchester City on final day of last season.
QPR, who narrowly avoided relegation last season, have one point from their opening two games of the 2012-13 campaign, which started with a 5-0 defeat at home to Swansea.
Marseille, meanwhile, lie top of France's Ligue 1 after three wins in their opening three matches.