Dulcie Wilmott was born in Adelaide in 1909. From 1926 to 1932 she studied at East Sydney Technical College under Rayner Hoff and attended painting classes at the J.S. Watkins Art School. In 1933 she married Geoffrey Collings and they had two daughters, Donna and the artist Silver Collings. She and her husband worked collaboratively for most of their lives, cosigning the majority of their work Dahl and Geoffrey Collings, the name Dahl having been coined by Geoffrey as a term of endearment.

The Collings travelled to London via Spain in 1935 taking many photographs and making their first documentary film in the medieval town of Alquézar in the Catalonian region of Spain. In London, Dahl worked as a freelance designer until László Moholy-Nagy offered her a job in his studio working on the Simpsons of Piccadilly menswear store project in 1936. There she gained first-hand experience of European modernism and of Moholy-Nagy’s and György Kepes’s approach to design which she and Geoffrey embraced wholeheartedly.

Back in Sydney, they established a commercial and industrial design studio with Richard Haughton James in 1939. It was one of the nation’s first design-focussed studios and Dahl was a pioneer in introducing modern design principles to local industry. During the 1940s she exhibited with the Contemporary Art Society and the Australian Commercial and Industrial Artists’ Association, winning (with Geoffrey) four ACIAA awards in 1940. Dahl was costume designer for the films Eureka Stockade (1949) and The Overlanders (1946).

In the 1950s the family moved to New York. Dahl became a design consultant to the Australian Trade Commission, in charge of the Australian Display Centre in the Rockefeller Center. Back in Sydney in 1953, she and Geoffrey established their own film company, Collings Productions, with many of the films she produced and directed winning international awards.

From 1971 Dahl devoted herself full time to painting. She had solo shows at the Bonython (1976) and Holdsworth (1977) galleries in Sydney and at the City of Hamilton Art Gallery in Victoria in 1982.