He held posts at Florida Memorial College, William Woods College, and Eastern Washington State College, before his appointment in 1972 as Michigan State University's associate professor of humanities. In 1985 Greaves was appointed to Florida State University's Courtesy Professorship of Religion and then to their Robert O. Lawton Distinguished Professorship of History in 1989. From 1993 until 2002 he was chairman of the department of history at Florida. In 1981 he was elected fellow of the Royal Historical Society and in 1987 to the American Philosophical Society. In 1991 he was appointed president of the American Society of Church History and he also served as president of the InternationalJohn Bunyan Society. His 1969 work The Puritan Revolution and Educational Thought was awarded the Walter D. Love Prize of the Conference on British Studies and his Society and Religion in Elizabethan England was shortlisted for the Robert Livingston Schuyler Prize of the American Historical Association. Greaves was awarded the Albert C. Outler Prize in Ecumenical Church History from the American Society of Church History for his 1997 work, God's Other Children: Protestant Nonconformists and the Emergence of Denominational Churches in Ireland, 1660–1700. Greaves wrote extensively on John Bunyan and he edited volumes 2, 8, 9 and 11 of Oxford University Press' The Miscellaneous Works of John Bunyan. He also wrote a trilogy on the British radical underground in Restoration Britain: Deliver Us from Evil, Enemies under His Feet and Secrets of the Kingdom. He also edited the three-volume work Biographical Dictionary of British Radicals in the Seventeenth Century between 1982 and 1984, for which he wrote more than 180 of its entries. At the time of his death he was writing a biography of Robert Ferguson.
Works
The Puritan Revolution and Educational Thought: Background for Reform.
Theology and Revolution in the Scottish Reformation: Studies in the Thought of John Knox.
Society and Religion in Elizabethan England.
Saints and Rebels: Seven Nonconformists in Stuart England.
Deliver Us from Evil: The Radical Underground in Britain, 1660-1663.
Enemies Under His Feet: Radicals and Nonconformists in Britain, 1664-1677.
Secrets of the Kingdom: British Radicals from the Popish Plot to the Revolution of 1688–1689.
John Bunyan and English Nonconformity.
God's Other Children: Protestant Nonconformists and the Emergence of Denominational Churches in Ireland, 1660-1700.
Dublin's Merchant Quaker: Anthony Sharp and the Community of Friends, 1643-1707.
Glimpses of Glory: John Bunyan and English Dissent.