He served in the Legislative Assembly of Ontario from 1963 to 1985 as a member of the Progressive Conservative Party, and was a cabinet minister in the governments of John Robarts, Bill Davis and Frank Miller.

[2] After serving as a backbench supporter of the Robarts government for two years, he was named to cabinet on November 24, 1966 as Provincial Secretary (Ontario) and Minister of Citizenship.

[4] Welch proved a likeable figure and a good speaker, and built a base of delegate support at the expense of rival candidate Darcy McKeough.

[5] Welch became part of the new premier's inner circle of advisors and was often used as a "fixer" in the Davis government, taking temporary placements in difficult portfolios as a crisis manager.

Welch was often forced to remain silent in the legislative question period, while ministers under his watch responded to members of the opposition.

The latter position gave him supervisory powers over the departments of Correctional Services, Consumer and Corporate Affairs and the Solicitor General.

The Progressive Conservatives were reduced to a minority government in the 1975 provincial election, but remained in power due to divisions among the opposition parties.

Welch was re-elected for the newly created Brock constituency, while the redistributed division of Lincoln was won by the Liberal Party.

Welch remained Deputy Premier throughout the legislative session that followed, and saw the position elevated to cabinet level by an order in council of June 21, 1983.