Ayew was deemed surplus to requirements by Marseille in the close-season and joined Lorient in July.
And the Ghanaian made the league leaders pay as he converted from the penalty spot in the 37th minute to cancel out Dimitri Payet's opener five minutes earlier after Marseille goalkeeper Steve Mandanda had felled Benjamin Jeannot.
Marseille pressed to no avail in their search for a winner in the second half, with Lorient holding on to ensure a stalemate that gives defending champions Paris Saint-Germain the chance to take over at the top with a win at Lille on Wednesday.
Meanwhile, 10-man Monaco ended a run of four league games without a win by overcoming struggling Lens 2-0 at the Stade Louis II.
The hosts went a man down in the 35th minute as Brazilian defender Wallace was sent off for a challenge Benjamin Bourigeaud, however, Lens could not capitalise on their numerical advantage and fell behind in the 64th minute courtesy of a Dimitar Berbatov penalty.
Berbatov coolly slotted home after being taken down by Jerome Le Moigne, yet that lead looked set to last all of five minutes as Lens were awarded a spot-kick of their own following Anthony Martial's foul on Adamo Coulibaly.
However, Pierrick Valdivia fired over on the rebound after seeing his penalty saved by Danijel Subasic, and Monaco made the game safe in the third minute of injury time, forward Yannick Ferreira Carrasco cutting in from the left and curling home with a fine effort.
While Monaco arrested their winless run, there was more misery for Nantes, who are now three games without a victory due to a 2-1 home defeat to Toulouse.
Denmark international Martin Braithwaite scored the winner with a half-volley at the far post five minutes from time to seal all three points for Toulouse after their opener from Issiaga Sylla had been cancelled out by Jordan Veretout's penalty.
