pale rider / the heavy horses
Between 1950 and 1956 Hugh O'Brian had work in about 20 Westerns. Though these are from the Golden Age of Westerns I confess that I haven't seen most of them. I recognize Vengeance Valley (1951) and Broken Lance ( 1954). Colin - over at Riding the High Country blog (https://livius1.wordpress.com/) is an expert on Westerns from the 40's and 50's and could likely have some information on some of them.
Amazingly, except for TV work, Hugh made next to NO Western films
between 1954 and 1990!
But Hugh's big break came in 1955 when he was offered the role of
Wyatt Earp in: