As a councillor, he chaired the Finance and Resources Committee and the North East of Scotland's Regional Transport Partnership, NESTRANS.

Stewart was the convener of the Scottish Parliament's Local Government and Regeneration Committee,[2] where he oversaw scrutiny of the Community Empowerment (Scotland) Act 2015.

Stewart was also a member of the Welfare Reform Committee and also sat on the Justice Sub-committee on Policing.

He was also involved in the Cross-Party Groups on Oil & Gas, Scots language, Nuclear Disarmament, Malawi and Tibet.

He also acted as Parliamentary Liaison Officer to Nicola Sturgeon from November 2014 until the dissolution of parliament in March 2016.