Thiago Silva converted a spot-kick after OM were reduced to 10 men before the break and Jeremy Menez wrapped it up in the second half as PSG smoothly advanced with striker Zlatan Ibrahimovic being rested.
Carlo Ancelotti's side took full advantage after Marseille defender Rod Fanni was shown a straight red card in the 28th minute for a foul on Menez in the box.
Thiago Silva converted the resulting penalty by wrong footing Steve Mandanda and OM, who won the last three editions of the competition, barely bothered the hosts.
Menez made it 2-0 five minutes into the second half, firing home from close range after collecting a brilliant Javier Pastore through-ball.
Marseille had a chance to reduce the arrears in the closing stages but Benoit Cheyrou's low free-kick from 30 metres smashed against Nicolas Douchez's left post.
PSG were joined in the last eight by Montpellier and Nice on Wednesday.
French champions Montpellier needed just a Jonathan Tinhan goal on the hour to prevail 1-0 at home to Girondins Bordeaux, who failed to level the match after Cyril Jeunechamps was sent off for the hosts eight minutes from time.
Olympique Lyon were knocked out 3-1 at Nice, conceding three goals in the opening 15 minutes.
Bafetimbi Gomis cancelled out Valentin Eysseric's opener, only for Mahamane Traore and Renato Civelli to score for Nice in the ninth and 15th minutes respectively after some awful defending by the visitors.
The Bastia v AJ Auxerre game was called off because of bad weather, with the French League having yet to set another date.
On Tuesday, Saint-Etienne, Troyes, Stade Rennes and Lille went through.
