He missed the 1975 season but returned to action by winning the 1976 Belgian cross country title. He failed to repeat his previous success at the 1976 IAAF World Cross Country Championships, coming 49th, although Belgium took the team silver medals. His teammate Léon Schots won the gold at the 1977 IAAF World Cross Country Championships and De Beck's 18th-place finish saw him share in the team title for a third time in his career. As the 1970s neared to a close, the performance of the Belgian team declined: De Beck was 26th at both the 1978 and 1979 races, with Belgium ranking fifth overall in each competition. After missing the 1980 season, he was only 64th in 1981. He was his country's best performer at the 1982 and 1983 World Cross Country Championships, finishing 17th each time.