The following information comes from the pages of the Charleston Manor collection of Birley's works.

Sir Oswald Birley was born in New Zealand on the 31st March 1880 son of Hugh Francis and Elizabeth Birley, a Lancashire family of the Mount, St. Asaph, North Wales. He later attended a traditional education at Harrow and Trinity College, Cambridge. He turned to painting whilst studying the Old Masters in Dresden and Florence and enrolled in the Academie Julien in Paris where he studied under the Beaux Arts trained master Marcel Basschet

In Paris he came under the influence of such painters as Bourguereau and his example and the proficiency which academic artists achieved in the late 19th century show in his earliest exhibited work, the superlative full-length nude which earned it's young painter an honourable mention in the Paris Salon of 1903.

After Paris Birley travelled in Spain and like many others fell under the influence of Velasquez and the golden age of Spanish painting. His "Rag Sorter" exhibited in 1905 and portraits of Mabel Beardsley as an Elizabethan page exhibited in 1915 exemplify this and also show the close affinity to Sargent which most of Birley's pre-work demonstrates.

On his return to London we find him at the St. John's Wood School of Art in the company of such artists as William Orpen and James Pride: Birley's tour-de-force "Interior of James Pride's Studio" is particularly reminiscent of Orpen's compositions. Glyn Philpot was another painter strongly influenced by Sargent, and working during this period in a similar vein to Birley.

World War I interfered and Birley enlisted in the 10th Battalion the Royal Fusiliers in September 1914 where he was gazetted Lieutenant after a short period in the ranks. He transferred, in June 1915, to the Intelligence Corps obtaining the rank of Captain in 1916 serving in France until 1919 when he was awarded the Military Cross.

After the war he resumed his earlier career and became well-established as a fashionable portrait painter. In 1921 he married an Irish beauty, Rhoda Vava Mary Lecky Pike, who was twenty years his junior. Rhoda was the daughter of Robert Lecky Pike of Kilnock, Thurlow, Co. Carlow, Eire. As could be expected, he painted many portraits of her, the best perhaps showing her striking profile.