Robert Dinwiddie Grigg Jr., 84, a life insurance salesman here for more than 40 years before his retirement in 1958, died of a heart attack Monday while at a family outing in Alexandria.

During his career with the Life Insurance Co. of Virginia, he had received awards almost every year for his large sales of policies to Washington area residents.

Born in Gainsville, Ga., Mr. Grigg joined a Florida vaudeville circuit as a singer while still a youth. He served as a hospital attendent in World War I and then worked briefly for the U.S. Air Mail Service in Washington before entering the insurance business. He earned a law degree from National University.

Mr. Grigg lived in Bethesda but in recent years had spent the winters in Acapulco, Mexico. He had been a vestryman and Sunday School superintendent at St. Luke's Episcopal Church in Bethesda, where he had sung in the choir.

He was a member of the Grand Masters of the Masons and the Shrine.

He is survived by his wife, Lillian Maurice Grigg, of the home; two sons, Robert D. III, of Bethesda, and William, of Chevy Chase, a daughter, Ida Jo McKenney, of New Concord, Ohio; a sister, Emily Urbins, of New Orleans, and five grandchildren.