More than 73,200 members are eligible to vote online or by phone.
The candidates to become leader of the sovereigntist party are members of the legislature Jean-Francois Lisee, Alexandre Cloutier and Martine Ouellet and the unelected Paul St-Pierre Plamondon.
Recent polls have indicated that Lisee and Cloutier are battling it out for first place, with Ouellet running third and Plamondon languishing in fourth.
The campaign has focused largely on issues of language, identity and Quebec sovereignty.
Only Ouellet has promised to hold a sovereignty referendum in a first PQ mandate should she win and become premier in the 2018 provincial election.
The race for the PQ’s top job is the second in less than two years after Peladeau cited family reasons when he quit last May, just one year after he became leader.