John W. Magruder, 76, a former county agent leader in the Maryland State Agricultural Extension Service at the University of Maryland, died Thursday at Prince George's General Hospital in Cheverly following a stroke.

Mr. Magruder was named a professor emeritus by the University of Maryland when he retired in 1963. He began his career with the extension service in 1928 as the Howard County agent.

His service in Howard County lasted until 1935, when he was transferred to the University of Maryland at College Park to become assistant director of rural rehabilitation. He then served a year as extension soil conservationist. From 1933 to 1948, he was extension agromist. He was county agent leader in charge of all Maryland extension agents from 1948 until his retirement.

Mr. Magruder was born on a farm in Gaithersburg. He graduated from the University of Maryland with a bachelor of science degree in agriculture and then moved to Howard County, where he taught vocational agriculture in the public schools before joining the extension service.

In 1940, he earned a master's degree in agronomy from Cornell University.

He was a member of the Maryland state Grange for almost 50 years. He also was a member of the Phi Kappa Phi honorary fraternity, and the University of Maryland Faculty Club.

Survivors include his wife of 44 years, Myrne Hendry Magruder, of the home in College Park; two sisters, "mrs. Willis L. Cissel, of Woodbine, Md., and Mrs. Garland Turner, of Rosanky, Tex., and a brother, Harry W. Magruder, also of Rosanky.

The family suggests that expressions of sympathy be in the form of contributions to the Agricultural Development Fund, c/0 the director of the Maryland Cooperative Extension Service, Simons Hall, College Park, Md., 20742.