In 1951 she took a position at the University of Chicago's Yerkes Observatory, Wisconsin, her first job in the United States. Her research during this period focused on the abundances of chemical elements in stars. She returned to the UK in 1953, when Margaret and her husband Geoffrey Burbidge were invited to work with William Alfred Fowler and Fred Hoyle at the University of Cambridge. The team combined data on elemental abundances produced by the Burbidges with Hoyle's hypothesis that all chemical elements might be produced in stars by a series of nuclear reactions, and Fowler's laboratory experiments on those reactions. The idea became known as stellar nucleosynthesis. They published their model in a series of papers, culminating in a magnum opus in 1957, now known as the B2FH paper after the initials of Burbidge, Burbidge, Fowler & Hoyle. Margaret Burbidge was the first author of the paper, which was written while she was pregnant. The paper demonstrated that most heavier chemical elements were formed in stellar evolution. The theory they developed remains the fundamental basis for stellar nucleosynthesis. Fowler was later awarded the 1983 Nobel Prize in Physics (shared with Subrahmanyan Chandrasekhar) for his work on nucleosynthesis, and expressed surprise that Burbidge was not included.