Upon graduation from Memorial University of Newfoundland (MUN), Mark served as a commissioned officer in the Canadian Navy before returning to Newfoundland to pursue studies as a professional accountant, attaining his designation in 1980. He was awarded the Fellow designation in 2001 for outstanding service to his profession and the community. He worked with Nalcor Energy for several years, serving as treasurer, controller, director of finance and finally as general manager finance - Lower Churchill Project. Mark retired in 2012 and formed MGB Professional Services, Ltd., a professional services company, and has provided consulting services focused on internal audit effectiveness.
He has been active in the accounting profession, having served as president of the Institute of Chartered Accountants of Newfoundland and Labrador in 2000, and on numerous committees and boards of directors.