During 14 years of service at the Massachusetts General Hospital (MGH), he became the director of Acute Psychiatric Service, director of Outpatient Psychiatry, and director of Clinical Services for the Department of Psychiatry while rising to the rank of Professor of Psychiatry at Harvard Medical School. During his tenure at MGH, Lazare built the outpatient psychiatry department into the largest and most diverse in New England, and provided leadership for founding and developing what many believe has been the most successful continuing education course in psychiatry in the U.S.