A lifelong breeder and owner of harness horses, from the 1940s to the 1970s, Percy Gray and his brother Jere, of Swansea, Massachusetts operated a successful stable. In 1947 and 1948 the Gray Stables, with trainer-driver Franklin Safford, practically swept the juvenile pacing events on the Grand Circuit with Knight Dream, a world champion both years. Other outstanding horses owned by the Grays included Knight Time, Parson's Bret and Glory. Percy Gray was a trustee of The Hall of Fame of the Trotter now known as the Harness Racing Museum & Hall of Fame. He died June 21, 1977 at age 86 in Fall River, Massachusetts.