Fabinho added a third just after halftime with a thunderous finish and new signing Kamil Glik rounded off the rout in the 71st minute before Julian Palmieri volleyed in a late consolation goal for the hosts.
The victory put Monaco top on 10 points, extending their lead over PSG, who were stunned on Friday when St Etienne bagged a stoppage-time equaliser to secure a 1-1 draw.
While Monaco's fine start to the season continued, Lyon slipped further off the pace after their defensive deficiencies were exposed by Bordeaux, despite taking a second-minute lead through Aldo Kalulu.
Malcom responded for the visitors with a long-range effort in the 33rd minute. After OL captain Maxime Gonalons was red carded in the 67th, Bordeaux's Gregory Sertic and Jeremy Menez found the net as Hubert Fournier's side dropped to sixth on six points.
(Reporting by Ed Dove; Editing by TOby Davis)
