;Bourassa government Trépanier was elected to the Quebec legislature in the 1985 provincial election, defeating Parti Québécois incumbent Huguette Lachapelle in the Montreal division of Dorion. The Liberal Party won a majority government in this election, and Trépanier entered the legislature as a backbench supporter of Robert Bourassa's administration. From December 13, 1985, to March 3, 1989, she was the parliamentary assistant to the minister of municipal affairs. She was promoted to the provincial ministry on March 3, 1989, serving as the junior minister responsible for cultural communities and immigration. She assisted Monique Gagnon-Tremblay, who held the full cabinet portfolio for these files. Trépanier was re-elected over PQ candidate Joseph Facal in the 1989 provincial election and was reassigned as the minister responsible for the status of women and minister responsible for the family on October 11, 1989. During ceremonies marking the fiftieth anniversary of women's suffrage in Quebec in April 1990, Trépanier said that the greatest challenge of modern Quebec women was to create a society where family and work were compatible. "What women need is day care, flexible work schedules, maternity leave, pay equity and a lot of vigilance because the gains we have made are very fragile," she said. Later in the same year, she introduced a bill allowing parents to take thirty-four weeks of unpaid parental leave after the birth or adoption of a child; she described the bill as the first step toward paid parental leave. She also ensured passage of a bill requiring that all divorcing couples in Quebec equally split the value of most shared assets developed during their relationship. Trépanier criticized the federal government of Brian Mulroney for cutting universal child care benefits and cancelling funding targeted to day care. She introduced legislation in April 1992 to guarantee mandatory child support payments in the event of a separation or divorce, create 7,500 new day care spaces in three years, and set aside $1.8 million for pilot projects to enhance family life. She also re-affirmed her support for Quebec's universal family allowance policy, intended to encourage couples to have more children, which was introduced shortly before she was appointed to cabinet. In late 1993, she introduced a new government policy document on women that proposed an employment equity law for all public sector and some private sector organizations with over one hundred employees. Some provincial groups representing women criticized the document as being for the most part vague and unspecific. Trépanier was the minister responsible for the status women at the time of the École Polytechnique massacre, in which lone gunman Marc Lepine shot and murdered fourteen women at the École Polytechnique de Montréal. In common with other female members of Bourassa's cabinet, Trépanier cautioned against interpreting the massacre as anything other than the act of a single psychopathic individual. ;Johnson government Trépanier supported Daniel Johnson's successful bid to succeed Robert Bourassa as leader of the Quebec Liberal Party and premier of Quebec in January 1994. When Johnson became premier on January 11, 1994, he appointed Trépanier to a full cabinet position as minister of revenue security. She also retained ministerial responsibility for the status of women and the family. In March 1994, Trépanier and employment ministerSerge Marcil announced a $17.2 million program to assist persons on social assistance in starting up small businesses. Critics charged that it would be ineffective as it required recipients to provide two thousand dollars in cash or goods toward their project; some argued this was an unrealistic sum. Trépanier later announced the expansion of a program that encouraged social assistance recipients to accept temporary jobs for non-profit organizations. Trépanier also announced in March 1994 that Quebec would increase its monthly breastfeeding subsidy from $15 to $37.50, while simultaneously reducing funds for milk formula, in an effort to encourage more low-income women to nurse their infants. This decision received international attention. She was not a candidate in the 1994 provincial election and formally resigned from cabinet on September 26, 1994. She became director of recruiting and financing for the Quebec Liberal Party in 2001 and still held this position as of 2010.
