Toko Ekambi, Bruno Guimaraes and Moussa Dembele found the back of the net to lift OL, who are not playing in Europe this season, up to third on 23 points from 12 games.
They trail leaders Paris St Germain, who were held to a 2-2 home draw by Girondins de Bordeaux on Saturday, by two points and are behind second-placed Lille on goal difference.
Lille missed out on an opportunity to move level on points with PSG when they were held to a 1-1 draw at St Etienne later on Sunday.
Monaco are fourth, also on 23 points, after goals by Sofiane Diop, Gelson Martins and Kevin Volland earned them a 3-0 home victory against Nimes for their fourth straight win.