Painter, printmaker, designer, and educator Claire Oak was born in St. Georges, Quebec, Canada, in 1921, one of ten children. At the behest of her parents she was required to earn a degree in teaching; after accomplishing this, she told them she wanted to pursue art, and they agreed to fund her enrollment at L'Ecole des Beaux Arts in Quebec. Following her graduation she moved to New York, where she attended the Art Students' League and studied design and printmaking. She worked for an advertising agency through whom her work appeared in Vogue, The New Yorker, Mademoiselle, Glamour, Harper's Bazaar, and more. In the late 1940s she traveled to Paris, France with her husband, radio announcer Alan Oak. There, she continued her fine art studies at the La Grande Chaumiere in Paris and worked for Parisian advertising agencies. She exhibited when possible, and made plans to form the Fashion Illustration Workshop, which she operated for a brief time after their return to New York.

The Oaks settled in Los Angeles in the 1950s. Claire continued to work as a designer, taking a freelance position at May & Co., supplying illustrations for Katten and Marengo. The Oaks relocated for the last time in the 1960s, this time to Stockton, where Oak took began teaching once more, traveling to Sacramento to instruct adult watercolor classes at Bauder College and San Joaquin Delta College. At this time she also attended courses at the San Francisco Art Institute. In addition to her work as an artist and designer, Oak was a collector of contemporary art and began buying and trading artworks with fellow artists in the late 1940s; upon her death in 2013 a collection of close to 2,600 works were found in her home.

Claire Oak won a variety of First Awards in national and regional shows. In 1982 she was awarded the Susan B. Anthony "Woman of Achievement in Creative Arts" medal by the University of the Pacific. She was a member of the Stockton Art League, Lodi Art Center, Central California Art League, and the Delta Watercolor Society. She is listed in Who's Who in America.

Oak died in October of 2013.