Beer served in the RAF from 1946 to 1948. He was a junior research fellow at St John's College, Cambridge, from 1955 to 1958. Between 1958 and 1964 he was assistant lecturer and then lecturer at the University of Manchester. From 1964 until his retirement in 1993, he was successively lecturer, reader (1978) and professor (1987) of English literature at the University of Cambridge. He was married to the literary critic Gillian Beer, DBE. He was president of the Charles Lamb Society from 1989 until 2002. He was a Leverhulme emeritus fellow in 1995–1996 and was the 2006 Stanton lecturer in the philosophy of religion in the University of Cambridge.