She qualified at Trinity College Dublin in 1953 and served on the Royal Society of Medicine's section on Epidemiology and Public Health. In her career she worked at several institutions in London including the Academic Department of Community Medicine at King's College Hospital Medical School, the Department of Community Medicine at St Thomas's Hospital Medical School and the London School of Hygiene and Tropical Medicine. In 1982 she served on the Faculty of Public Health Medicine of the Royal College of Physicians of the United Kingdom.
Her medical school, Trinity College, celebrated its Tercentenary in 2011; she joined the Tercentenary Board.
Bewley was made Dame Commander of the Order of the British Empire in 2000 New Year Honours for services to public health, and in recognition of her leading role in promoting equal opportunities for women. She was conferred with an Honorary LLD by Trinity College Dublin in 2002.
- The Inadequacy of Adolescent Health Statistics, Oxford Journal of Public Health
- Beulah-Bewley: My Life as a Woman and Doctor (autobiography; ISBN 978-17813-241-96) 
- As early as 1902 Ballantyne had found an increase in the abortion rate in French and Austrian women working in tobacco factories. - Beulah R. Bewley, "Smoking in Pregnancy", British Medical Journal (Vol. 288, Issue #6415, pp 424–426, 11 February 1984)
- "There certainly was discrimination. They used to look at you and say she is married, or she has got children and if you were not married, they were expecting you to get married." (B. Bewley)
- "Promotion by tobacco companies may then be seen for what it is—the ‘pushing' of a dangerous drug." — B. Bewley