Laura Handly (Muffet) Brock, 49, the wife of U.S. Labor Secretary William E. Brock and a past treasurer of the Senate wives chapter of the American Red Cross, died of cancer yesterday at Georgetown University Hospital. She lived in Washington.

She was a native of Chattanooga, Tenn., and a graduate of Briar Cliff College in Sioux City, Iowa. She and Mr. Brock were married in January 1957. She moved here following his election in 1962 to the House of Representatives.

Mrs. Brock served as 1985 hospitality chairman of the International Neighbors Club and was a member of the executive panel of the National Business Consortium for the Gifted and Talented. She also had chaired the Women's Federal Forum.

She was a member of the Congressional Club and of the mothers' clubs of St. Patrick's School, the National Cathedral School and St. Albans School for Boys. She attended St. Alban's Episcopal Church in Washington. In Tennessee, she was a member of the National Society of Colonial Dames and a sustaining member of the Junior League of Chattanooga.

After serving four terms in the House, her husband represented Tennessee in the U.S. Senate. He also was chairman of the Republican Party and U.S. trade representative before becoming labor secretary in March.

In addition to her husband, of Washington, survivors include a daughter, Laura (Hutchie) Brock, also of Washington; three sons, William, of Chattanooga, and John and Oscar, both of Washington, and three grandchildren.