Margaret Mary Conner earned a BA in home economics from the State University of Iowa (now the University of Iowa) in 1934. She then earned an MS in nutrition from the State University of Iowa in 1939 and pursued additional graduate study at Columbia University. When the nutrition division of the New York City Department of Health was established in 1943, she became one of the division's first nutritionists. She was responsible for making radio broadcasts on WNYC titled "Listen to Nutrition," a popular mass-education program. She also taught nutrition to medical workers and served on a wartime medical board that awarded more ration points to the ill and the elderly. Conner and her staff prepared courses for school children, worked in mobile demonstration kitchens, and wrote a monthly bulletin for the city (see Department of Home Economics Newsletters, University of Iowa Department of Home Economics Records, for more information).

In 1957, Conner was honorerd by the Public Health Association of New York City for providing outstanding service in the field of nutrition. In 1962, she became the principal nutritionist for the public health nutrition program of the city of New York's Department of Health under a provisional appointment, which became permanent in 1964. During her tenure, she helped to expand prenatal nutrition programs, institute emergency pediatric services in underserved areas, and tailor nutrition programs for children with physical disabilities. She presided over the rapid expansion of the department and harnessed the energies of her staff to provide services for the new Head Start program. Conner retired in 1971.

Conner authored many departmental publications, including its history, "Retrospect, Introspect, Prospect." In 1963, she won the prestigious Lydia J. Roberts Essay Award offered by the American Dietetic Association for her essay, "A History of Dietary Standards." (Journal of the American Dietetic Association, 1963, p. 564.)