When Louis Fieser left Bryn Mawr in 1930 to join the faculty at Harvard University, Mary Peters decided to follow him and pursue an advanced degree in chemistry.

She had to officially enroll at nearby Radcliffe College in order to take chemistry courses at Harvard and could not escape the gender discrimination of her era.

[1] One professor of analytical chemistry in particular, Gregory Baxter, would not allow her in the laboratory with the male students: rather, she had to carry out her experiments (without supervision) in the deserted basement of a nearby building.

[12] Fieser never had a paid position at Harvard, although she received the title of Research Fellow of Chemistry about twenty-nine years after she began work there.

[1] She was awarded the Garvan Medal of the American Chemical Society in 1971,[13] and the Louis and Mary Fieser Laboratory for Undergraduate Organic Chemistry at Harvard University is named after her and her husband.