Mrs. William C. Grayson of Upperville, Va., and Washington, D.C. has announced the engagement of her daughter, Katherine Mary, to Fraser Bryan Wilkins, son of the Honorble Fraser Wilkins of Washington, D.C.

Miss Grayson, Development Assistant to the Director of Mount Vernon, the home of George Washington, is a graduate of Foxcroft School and Yale University, 1977. She is a partner in her family's operation of Blue Ridge Farm near Upperville. Her father, the late William Cabell Grayson, was special coordinator for telecommunications at the Smithsonian Institution. She is the granddaughter of the late Admiral Cary T. Grayson, personal physician to Woodrow Wilson and the late Mrs. George L. Harrison. She is also the granddaughter of Mrs. George Ketchem of Pittsburgh, Pa., and Hobe Sound, Fla., and the late Mr. Ketchum, who founded Ketchum, MacLeod & Grove, Inc.

Mr. Wilkins is a Washington correspondent for Fairchild Publications as well as managing partner of Moxley Farm, Shelbyville, Kentucky. He graduated from St. Paul's School and the University of Pennsylvania, 1973.

His father, a retired Foreign Service Officer, was Ambassador to Cyprus and Inspector-General of the Foreign Service. His mother, the late Anne Bryan Wilkins, was the daughter of Mrs. Hamilton Vose Bryan of Washington, D.C. and Shelbyville, Ky., and of the late Cdr. Bryan. Mr. Wilkins is also a grandson of the late Mr. and Mrs. Harry F. Wilkins of Omaha, Neb.

They are planning to be married in May.