[1] She studied with William Thompson Sedgwick at the Massachusetts Institute of Technology, where she became the first woman to receive a degree in biology from MIT.

After she completed her post-graduate studies in Harvard University O'Grady worked as an assistant to the zoologist Edmund Beecher Wilson at Bryn Mawr College in Pennsylvania.

During this time O'Grady was very much in favour of encouraging women to study and advance themselves in higher education.

In 1896 she visited Würzburg, at a time when women were not allowed to study at university in Germany, where she met her future husband.

[2] Her husband died in 1915, from tuberculosis, which Marcella was convinced was aggravated by stress due to the First World War.