A Nabil Fekir goal was enough for Lyon to beat Nantes 1-0 on Sunday and move back to the top of the Ligue 1 table, while Marseille had to settle for a 2-2 draw at Saint-Etienne.
Lyon broke the deadlock midway through the second half against Nantes at the Stade de Gerland when Yoann Gourcuff and Alexandre Lacazette combined to set up Fekir, and he was credited with the goal despite defender Kian Hansen appearing to get the final touch.
It was Lyon's first attempt on target but the goal allowed them to make it 11 league games without defeat as they reopened a two-point gap to reigning champions Paris Saint-Germain, who briefly went top after beating Toulouse 3-1 on Saturday with Adrien Rabiot scoring twice.
"It is a relief after a difficult match against a well-organised Nantes team who left us very little space," said OL coach Hubert Fournier, whose side now have consecutive away games to come at Lille, Montpellier and Marseille.
"This victory was important before we have three straight away matches against difficult teams. It would be wiser to wait until after these games to see if we can still trouble Paris and stay on the podium."
Lyon had drawn their last three matches in the absence of 21-goal leading scorer Lacazette, but he returned after a hamstring injury to lead the line against a Nantes side still looking for their first league win of 2015.
In a game of few clear chances, Lyon almost broke the deadlock five minutes before the interval as Fekir crashed a free-kick against the junction of bar and post.
Apart from that, Nantes 'keeper Remy Riou was never really troubled until the goal, although he was called into action to deny substitute Clinton Njie before he conceded a penalty in stoppage time for bringing down Fekir in the box.
However, with the last kick of the game, Lyon captain Maxime Gonalons missed the opportunity to score his first Ligue 1 goal in over two years as he put the penalty wide.
Erding denies Marseille
That result piled the pressure on faltering Marseille, and Marcelo Bielsa's side end the weekend in third place, four points off top spot, after they drew 2-2 at Saint-Etienne despite a brace from substitute Michy Batshuayi.
They fell behind when Max-Alain Gradel converted a 54th-minute penalty at the Stade Geoffroy-Guichard after Jeremy Morel brought down Romain Hamouma in the box.
However, a triple substitution just after the hour mark by Bielsa turned the game on its head.
Belgian striker Batshuayi replaced Andre-Pierre Gignac and equalised 55 seconds later with practically his first touch before finishing off a low cross from fellow substitute Romain Alessandrini to make it 2-1 on 67 minutes.
Yet Saint-Etienne hit back in injury time when another substitute, Mevlut Erding, headed in from practically on the line following a scramble in the Marseille penalty box.
Top of the table at Christmas, Marseille have taken just nine points from seven games in 2015 and have not won away from home in 10 attempts in all competitions since early October.
As a result, Marseille end the weekend outside the top two for the first time since early September.
"There is frustration because the win was within our grasp," said Bielsa.
Elsewhere on Sunday, Montpellier boosted their chances of qualifying for Europe with a 2-0 win against Guingamp in Brittany.
Morgan Sanson and Kevin Berigaud got the goals for the visitors and condemned Guingamp to a first defeat in eight games in all competitions and a first loss at home since November.
Meanwhile, Metz remain bottom of the table on goal difference after seeing their run without a league win extended to 14 games as they drew 0-0 at Reims.
Amongst the other games this weekend, Monaco warmed up for their Champions League trip to Arsenal on Wednesday with a 1-0 win at Cote d'Azur rivals Nice that leaves them in fourth spot.