Ronaldo's two goals made him the Champions League's top scorer with six goals. He opened the scoring in the fifth minute with a free kick from 30 yards and added a late insurance goal. He also hit the post and had another effort fisted out by goalie Steve Mandanda.
Raul Albiol scored what proved to be the winning goal for Real in the 60th minute.
Argentine Lucho Gonzalez scored in the first half for OM to tie the score but missed a chance to put the French club level again in the second half when he failed to convert a penalty kick.