Margaret Brackenbury Crook was born in Dymock, Gloucestershire, England on May 5, 1886 to Ellen Brackenbury Crook and Rev. L.G. Harris Crook. She attended St. Anne's School at Oxford, and received her BA with first class honors in 1913 from the University of London, since at that time Oxford did not grant degrees to women. Crook also earned a diploma with distinction in anthropology in 1914 from Oxon. In 1917, she received a certificate from Manchester College, Oxford, and was first in the college on completion of the three year course of study. From 1916-17, she went to France to work for the Society of Friends War Victims Relief Committee in the Marne and the Meuse.

In June of 1917 Crook was formally received into the ministry of the Unitarian and Liberal Christian Churches. In 1918 she became the minister of the Octagon Chapel in Norwich, England for two years. She was the first English woman to have entered in the training for the ministry and to have had sole charge of a large church. In 1920 Crook left England for America and became the executive secretary of the U.S. branch of the Women's International League for Peace and Freedom. In 1921 she was appointed Associate Professor at Smith College, a position that she held for 33 years. In 1938, Crook became a U.S. citizen. Her primary field of research was old testament studies, and she published a variety of books, articles, and essays on the subject, including: (1934), (1956), and (1964). She also edited and partially authored (1937).

In addition to her academic work, Crook was heavily involved in a variety of organizations. She was a member of the St. Anne's Society, the Society of Biblical Literature and Exegesis, the National Association of Biblical Instructors, the American Association of University Professors, served as the Smith College representative on the Corporation of the American Schools of Oriental Research, was an honorary lecturer at the Jerusalem school of Oriental research during the summer of 1934, served as president and honorary secretary of the Alumni of the American Schools of Oriental Research in 1943, 1942. She also served as president of the Women's Alliance of the Unitarian Church of Northampton and Florence Massachusetts.

Crook retired from Smith College in 1954. She never abandoned her scholastic pursuits. For 8 consecutive years she was named Sophia Smith Fellow of Smith College, an honor which was bestowed upon emeritus professors who have served the college and who continue to engage in scholarly projects. Crook lived in Northampton with her brother Waldo, who took care of her for the last few years of her life when her health began to fail. She died on May 24, 1972, after a brief illness. At the time of her death she had completed a book-long manuscript on the life and thought of the Apostle Paul.