She was born in Australia to British parents, Francis Edward Joseph and Isabella Eliza Butter Joseph (née Carnegy). Her mother came from a titled Scottish family. Her father, Patrick Carnegy of Lour, was a descendent of David Carnegie, 2nd Earl of Northesk. The family later adopted the Carnegy surname after Isabella succeeded to her father's estates in 1915. Beryl was educated privately in England and France.
In 1910, she joined the St John Ambulance Brigade and rapidly rose through the ranks. On the outbreak of the First World War she was put in charge of the Naval and Military Volunteer Aid Detachment (VAD) Department, which administered the combined nursing staff of St John Ambulance and the British Red Cross Society. She held the post throughout the war, but resigned in 1922 in opposition to plans to disband the VADs. She later joined the British Red Cross Society as head of its VAD department. She was credited with keeping the British Red Cross alive after the First World War, as she was later eulogised by a friend in The Times.
|“||Between the two world wars it was largely Lady Oliver's enthusiasm and untiring work which kept the British Red Cross active. It was thanks to her insistence on the importance of recruiting and maintaining the training of members of voluntary Aid Detachments at a high pitch after the 1914-18 War — despite its being considered the War to End Wars — that these members were in a position to answer the innumerable calls which came at a time when their services were so urgently needed in Hospitals and First Aid Posts at the outbreak of the Second World War.||”|
|— A.L., letter to The Times, 19 July 1972|
During the Second World War she was a member of the Society's War Organisation Executive Committee and several other committees. After the war she became the Society's Director of Education, retiring in 1956. She then became the BRCS's archivist and published its definitive history, The British Red Cross in Action, in 1966. She published a second book, The Church of Saint Mary the Virgin, Aldermanbury, in 1969.
In recognition of her work in the First World War, Oliver was awarded the Royal Red Cross (RRC) in 1916, and appointed Commander of the Order of the British Empire (CBE) in the 1919 New Year Honours and Dame Commander of the Order of the British Empire (DBE) in the 1920 civilian war honours. In recognition of her work in the Second World War, she was appointed Dame Grand Cross of the Order of the British Empire (GBE) in the 1948 New Year Honours. After the King invested her as a Dame Grand Cross, the Queen, as President of the British Red Cross Society, presented her with a diamond brooch at a party at Buckingham Palace.
- "Dame Beryl Oliver: Devoted service to Red Cross". The Times (The Times Digital Archive). 15 July 1972. p. 16.
- "Beryl Oliver". Oxford Dictionary of National Biography. Retrieved 25 March 2016.
- "Dame Beryl Oliver". The Times (The Times Digital Archive). 19 July 1972. p. 14.
- The London Gazette: . 1 February 1916.
- The London Gazette: . 8 January 1919.
- The London Gazette: . 26 March 1920.
- The London Gazette: . 30 December 1947.
- "Presentation To Dame Beryl Oliver". The Times (The Times Digital Archive). 11 February 1948. p. 6.