Grace Cady Coy, 75, a longtime resident of the Washington area who was active in volunteer work, died Sunday at Georgetown University Hospital. She had amyloidosis, a metabolic disorder.

Mrs. Coy was a native of Indiana and a graduate of Franklin College there. She taught elementary school in Indiana and was reporter with the Delphi Citizen in Delphi, Ind., before moving to Washington about 1940.

In the 1950s, she lived in New Mexico, where she served on the board of directors of the Albuquerque Broadcasting Company. She then returned to Washington.

During her years in this area, Mrs. Coy did volunteer work in foster care and family and child services. She received awards from the United Community Services organization and the National Association of Social Workers. She also had been an assistant secretary of the Eugene and Agnes E. Meyer Foundation.

Mrs. Coy had been a consultant to both the Labor Department and the Peace Corps.

She was the widow of Wayne Coy, a retired government official and broadcast executive, who died in 1957.

Mrs. Coy's survivors include two sons, Stephen, of Saratoga Springs, N.Y., and Wayne Jr., of Washington; a brother, John Cady of Athens, Ohio, and three grandchildren.

The family suggests that expressions of sympathy be in the form of contributions to the American Lung Association in Washington.