Philippe Couillard, Raymond Bachand and Pierre Moreau focused on education and labour issues in Sunday's leadership debate.
Couillard, who was Liberal health minister until he left for the private sector in 2008, suggested setting up a code of ethics for the Quebec Liberals to keep his party in check.
Moreau, a former transport minister, says he's open to making changes to the province's junior college system, while Bachand, a former finance minister, ruled out strengthening the province's language laws.
Polls have placed Couillard as the front runner to replace former premier Jean Charest at the head of the party.
Charest stepped down after the pro-independence Parti Quebecois won enough seats to form a minority government in last September's provincial election.
Delegates will elect the new Liberal leader during a congress in March.