First term (1987–1990)

She was elected for the riding of Fort William in the provincial election of 1987, defeating incumbent Progressive Conservative Michael Hennessy by 1,463 votes.^[2] The Liberals won a landslide majority in this election and made several historical breakthroughs in Northern Ontario. McLeod was appointed Minister of Colleges and Universities on September 29, 1987.^[3] Following a cabinet shuffle on August 2, 1989, she was named Minister of Energy and Minister of Natural Resources.^[4]

The Liberals were upset by the New Democratic Party in the provincial election of 1990, although McLeod was able to retain her riding against a strong challenge from NDP candidate Dan Hutsul, winning by 1,345 votes.^[5] Unlike most other Liberal candidates in this election, McLeod was supported by prominent members from the Ontario Secondary School Teachers' Federation in her region.

Second term and Ontario Liberal Party Leadership (1990–1995)

Peterson personally lost his seat in the 1990 campaign, and the Liberal party went through a series of interim leaders before holding a leadership convention in early 1992. McLeod was one of six candidates for the position, and was widely regarded as the main challenger to frontrunner Murray Elston. She finished a strong second on the first ballot, and overtook Elston on the third with support from Steve Mahoney's delegates. McLeod's people had made a deal with second-tier leadership contender Charles Beer. The Elston camp had an unexpectedly large lead on the first ballot, as McLeod lent Beer some of her delegates to give him a respectable showing, and Elston's margin dropped significantly when the eliminated Beer threw his full support behind McLeod.^[6] McLeod finally defeated Elston by nine votes on the fifth ballot, becoming the first woman to lead a major party in Ontario.^[7]

1995 provincial election campaign

With Bob Rae's NDP government being widely blamed for mishandling the major recession, McLeod's Liberals held a steady lead in the polls for most of the period from 1992 to 1995, and were generally expected to win the 1995 campaign. The party, however, damaged its credibility through a series of high-profile policy reversals in the period leading up to the election.

The most notable of these occurred when McLeod withdrew Liberal support for the proposed Equality Rights Statute Amendment Act (Bill 167), which would have granted same-sex couples most of the same rights as opposite-sex common law couples, introduced by the NDP government of Bob Rae in 1994. The legislation was defeated after the majority of Liberal MPPs and twelve NDP MPPs joined with the entire Progressive Conservative caucus in voting against it.^[8] Many regarded McLeod's decision as cynical and opportunistic, and some believe that it was intended to boost Liberal fortunes in rural areas following a by-election loss in the rural, socially conservative riding of Victoria—Haliburton. The result, however, was that the party earned a reputation for "flip-flopping" and inconsistency, while offending its socially progressive supporters.

McLeod also offended some immigrant voters, an electorally important group for Liberals, by criticizing the Rae government's handling of Somali refugee claims. Her intent was to draw attention to criminal gangs that were forcing Somalis to move to Ontario and defraud the provincial welfare system. Several, however, interpreted her criticisms as being directed toward the entire community.

During the campaign itself, McLeod further alienated many voters with an overly aggressive performance in the party leaders' debate, clashing with Premier Bob Rae and waving her party's platform before the cameras on several occasions. Prior to this performance, provincial Liberal support was regarded by many political insiders as soft and unsteady. After the debate, many voters who were previously leaning to the Liberals shifted to Mike Harris's Progressive Conservatives, who were in third place in the legislature. The Tories surpassed the Liberals to grab the swing in support away from the NDP and finished with a majority, while the Liberals finished with less support than the previous campaign and managed only 30 out of 130 seats.^[9]

McLeod herself was easily re-elected in Fort William, defeating Thunder Bay municipal councillor and Tory candidate Evelyn Dodds by over 8,000 votes.^[10] Some Liberals called on McLeod to step down after the election, and she announced her resignation as party leader two months later.

Third term (1995–1999)

McLeod remained a prominent Liberal MPP under new leader Dalton McGuinty, serving as education critic from 1996 to 1999. She was generally regarded as successful in this role, and proved an able opponent of Education Minister John Snobelen's restructuring policies.

Fourth term (1999–2003)

McLeod was re-elected by a landslide in the provincial election of 1999, in the redistributed riding of Thunder Bay—Atikokan.^[11] The Tories won the election with a reduced majority, and McLeod swapped shadow cabinet portfolios with Gerard Kennedy to serve as her party's health critic in the legislature that followed. She did not seek re-election in 2003.