"Ted Mack's Original Amateur Hour": DuMont (1948-49), NBC
(1949-54), ABC (1955-57), NBC (1957-58), CBS (1959, overlooked
is the first Sunday-afternoon version of the show in the fall of 1958
and winter of 1959), ABC (1960), CBS (Sunday afternoons, 1960-70).
"GE College Bowl": CBS (1959-63), NBC (1963-70).
"Password": CBS (1961-67), ABC (1971-75), NBC (as "Password Plus"
1979-82 and as "Super Password" 1984-89).
"Pyramid": CBS (1973-74), ABC (1974-80), CBS (1982-88)
"The Edge Of Night": CBS (1956-75), ABC (1975-84)
"Search For Tomorrow": CBS (1951-82), NBC (1982-86)
"Let's Make A Deal": NBC (1963-68), ABC (1968-76), NBC (1990),
CBS (2009-present)
"Match Game": NBC (1962-69), CBS (1973-79), ABC (1990-91) (also
part of NBC's "Match Game/Hollywood Squares Hour" in 1983-84)
And to get to primetime:
"JAG" started on NBC in 1985, lasted one season there, then moved to CBS.
"The Jeff Foxworthy Show": ABC (1995-96), NBC (1996-97)
"Ripley's Believe It Or Not": NBC (1949-50), ABC (1982-86)
"The Steve Allen Show/Comedy Hour" (I'm listing only his primetime variety shows):
CBS (1950-52), NBC (1956-60), ABC (1961), CBS (1967), NBC (1980-81)