Marg has earned her B.A., B.Ed. and M.Ed. from the University of Toronto, MA from the University of San Carlos, Guatemala, and her PhD from the University of Kansas. She has worked as a teacher for emotionally disturbed children in the late 50s and for the Toronto Board of Education till 1971. Since 1971, she has served as an assistant professor, associate professor, and professor in the Department of Special Education at the University of British Columbia, Vancouver, Canada. Between 1994 and 2001, Marg established undergraduate and graduate training for special education teachers at the University of Darussalam, Brunei. She is also an advisor to the Minister of Education in establishing programs for special education in the Brunei public schools. Marg has held the role of an editor of the International Journal of Special Education and is its Past President (1985-1989). She is a representative of the Department of Educational and Counseling Psychology and Special Education of the University of British Columbia and of the Association of Professors Emeriti.

Marg’s special assignments include: Lesotho (USAID), Nigeria (UNESCO), Indonesia and British Honduras (Canadian Teachers' Federation, Project Overseas). She is a life member of IASE.