Looking to bounce back from a poor run of form with only one win in their previous five games, Marseille attacked from the first whistle in search of an early goal.
The best early chance fell to Pierre-Emerick Aubameyang after a fantastic first touch to control a lofted ball over the top. Still, the onrushing Radoslaw Majecki did just enough to put him off as the finish drifted wide of the far post.
Brest did have a chance of their own moments later when Pathe Mboup found time and space in the box, but his near-post drive was well-saved by the legs of Geronimo Rulli.
Despite showing no attacking ambition, the visitors started to settle into the game, only to gift Marseille the lead midway through the half.
An Angel Gomes free-kick from 20 yards didn’t appear to pose any threat as it flew straight at Majecki, but the Polish keeper allowed the ball to hit both of his hands before it looped up and dribbled over the line.
The self-destruction continued on the half-hour mark when Kenny Lala barged Igor Paixao over in the box, and Mason Greenwood calmly tucked the resultant penalty home as the hosts went into the break 2-0 up.
Despite making a double change at the break, Brest struggled to mount any attacking pressure as the hosts looked comfortable in their lead.
Greenwood came close to adding a second as his low drive was tipped behind by Radosław Majecki. Marseille were able to add some gloss to the scoreline in the final 10 minutes, as Aubemayang swept home after strong work down the right from Matt O'Riley.
The three points see Marseille leap to the top of the table, albeit only one point ahead of PSG and having played a game more. On the other hand, failing to win in six games sees Brest hovering just one point above the drop zone, with all of their rivals still to play this weekend.
Flashscore Man of the Match: Angel Gomes (Marseille)
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