Party members had until 5 p.m. ET to cast a ballot for either Péladeau, Alexandre Cloutier or Martine Ouellet.
Cloutier and Oullet were both cabinet ministers under Marois, who resigned as PQ leader after the party's April 2014 election defeat.
The vote count is underway, and the results are expected around 9 p.m.
If none of the three candidates gets more than 50 per cent of the ballots cast, the candidate with the least number of votes will dropped from the ballot, and there will be a runoff vote between the two remaining contenders for the leadership job next week.