A member of the governing Liberal Party, Alcock currently belongs to the Cabinet of Canada, serving as President of the Treasury Board.
Alcock has served as the Chair of the House of Commons Standing Committee on Human Resource Development and the Status of Persons with Disabilities. He was also a member of the Standing Committee on Justice and Human Rights and Chair of the Manitoba Liberal Caucus.
Alcock is the former director of Manitoba Child and Family Services, and a former president of a private consulting firm.
From 1988 to 1993, Alcock was the Liberal Party of Manitoba member of the Legislative Assembly, and was the house leader between 1988 and 1990.