I can think of some I watched back then on the 50s, for loose, very loose, definitions of science fiction, although the last two in the list were pretty good, more..hmmm..science fantasy/horror.
Flash Gordon (One of my cats is named after Ming...the Merciless, Flash Gordon's nemesis. He's a rather aggressive and "catcho" tomcat)
One Step Beyond
Kraft Mystery Theater
There's probably more, and certainly a ton of sci fi movies from back then, but those are the TV shows I remember readily.