Attorney McElroy is a 1976 magna cum laude graduate of the University of Notre Dame in South Bend, Indiana, and a 1979 cum laude graduate of Boston College Law School. He was admitted to practice in 1979 and is licensed to practice before the United States Supreme Court.

From 1979 through 1985 Attorney McElroy was an Assistant District Attorney for Norfolk County where he handled trials in the District and Superior Courts, as well as appellate work. He joined Cosgrove, Eisenberg and Kiley, P.C. in November of 1985; he became a partner of the firm in July 1990. He concentrates his practice in civil and criminal litigation, with an emphasis on personal injury and worker's compensation matters.

Attorney McElroy has served on the Executive Committees of the Quincy and Norfolk Bar Associations. He is a past President of the Quincy Bar Association.  He has served as a trial advisor with the Harvard Law School Trial Advocacy Program since 1982 and is a member of the Massachusetts Academy of Trial Attorneys and the American Association for Justice, the Norfolk Bar Association and the Massachusetts Bar Association.  He is a Massachusetts Bar Foundation Fellow, and a past member of the House of Delegates of the Massachusetts Bar Association.