He also appeared opposite Charlton Heston in the science fiction film The Omega Man, in a sympathetic co-starring role.

After a solid supporting part as a Jewish concentration camp survivor in the critically acclaimed Voyage of the Damned (1976), as well as the mayor in Heaven's Gate (1980), he began a long run of portraying villainous types in productions such as Roots: The Next Generations and The Glitter Dome.

14) magazines, Koslo spoke about his experiences working in several films with Charles Bronson and in The Omega Man with Heston.

Starting in the late 1970s, Koslo appeared (usually as a villain) in a string of television shows such as The Rockford Files, Mission: Impossible, Barnaby Jones, The Incredible Hulk, Quincy, M.E., Buck Rogers in the 25th Century, T. J. Hooker, The A-Team, The Fall Guy, Dallas and Hunter.

He was also in Loose Cannons (1990) and appeared as the Russian battle-robot pilot Alexander in the science fiction film Robot Jox (1990).