Gregory continued in Formula One until 1965, but mainly with uncompetitive independent teams. He was unable to reproduce the results he obtained early in his career, his best being a sixth at the 1962 United States Grand Prix at Watkins Glen with the UDT Laystall team, in a Lotus 24. Running fourth, just behind eventual winner Dan Gurney at the French Grand Prix, Gregory retired with ignition problems, losing possibly his best chance at a maiden Grand Prix victory. Gregory did manage a win in the non-Championship 1962 Kanonloppet race at Karlskoga in Sweden, but this race did not feature any top teams.