The Parti Québécois won a historic majority government in this election, and de Belleval was appointed to René Lévesque's first cabinet on November 26, 1976, as minister of the public service and vice-president of the treasury board.
[6] De Belleval argued in April 1978 that Quebec's hiring laws should be modified to facilitate the entry of more anglophones into the civil service.
The provincial cabinet had previously been divided on the issue of English-language education, and Lévesque agreed to de Belleval's formula as a compromise.
[14] De Belleval later issued an alternate proposal that Nordair purchase Quebecair in a "reverse takeover" that would lead to a merger.
De Belleval was re-elected without difficulty in the 1981 provincial election as the Parti Québécois won a second majority government across the province.
[16] It was rumoured that he might return to cabinet in 1982 after he submitted a twenty-page policy paper proposing a "solitary fund" for development to be administered jointly by business, labour, and the state.
[18] De Belleval oversaw federally owned harbour land in Montreal and Quebec City during his time as president of Ports Canada.
[19] The Mulroney government subsequently appointed de Belleval as president and chief executive officer of Via Rail, with a term starting on July 1, 1987.
De Belleval responded with a forceful appeal in defense of the sector that argued that rail service was vital to Canada's transport needs and rejected suggestions that public money would be better spent on road construction or upgrades to air travel.
[24] Promoting long-term strategies such as a high-speed link between Montreal and Toronto and increased tourist travel, de Belleval urged the Mulroney government to maintain its existing levels of support.
[26] De Belleval's efforts were ultimately unsuccessful, and the Mulroney government announced in April 1989 that it would cut Via's subsidy by five hundred million dollars over the next four years.
He described the city's deal with Quebecor with a phrase translating as "worthy of a banana republic" and announced in April 2011 that he would seek to nullify it via a court challenge.