Marseille remain top of Ligue 1 after maintaining their 100% record with a narrow victory at Nancy on Sunday.
OM scraped a 1-0 success at Stade Marcel-Picot to make it five wins from five for the title hopefuls.
Jordan Ayew was the match-winner, finding the target after 57 minutes.
Lyon remain two points off the pace in second, courtesy of a routine 2-0 win over Ajaccio at Stade Gerland.
Dejan Lovren (25) and Lisandro Lopez (74) scored the goals as Les Gones enjoyed their fourth win of the season.
Lorient preserved their unbeaten start to the Ligue 1 season with a 2-1 victory at Rennes in a controversial affair which saw three players sent off.
Two goals from Alain Traore put the visitors in the driving seat but that was tempered by red cards for Maxine Baca and goalkeeper Fabien Audard.
Rennes replied through Jonathan Pitroipa but they also finished the match a man less with Cheick Diarra given his marching orders.