Following his call to the Bar in 1968, William J. MacLeod worked for a large law firm in Toronto. He moved to Oakville in 1971 where he set up private practice. By 1991, he had expanded his firm to more than 10 lawyers at which time it merged with another law firm of the same size to form the largest law firm in Halton Region. In 1996, he decided to resume practice as a sole practictioner in order to continue to provide his clients with the personal service he preferred.
William J. MacLeod became very active in the Oakville community. He is a past President of the Oakville Chamber of Commerce, was a board member for the United Way of Oakville and the 1995 Campaign Chair for the United Way. He was a founding director of the Oakville Community Foundation and still remains very involved as a member of the Advisory General.
He was also a founding and long standing member of Home Suite Hope Shared Living Corp. a charity which creates affordable transitional housing in Halton for people who are homeless or in a housing crisis. His community involvement extended to several other charitable organizations including Oakville Waterfront Festival, Lions Club and Lions Homes for Deaf People which took the form of both active board participation and pro bono legal services.