According to Tony Thomas's book on The Films Of Dick Powell, Zane Grey was Powell's favorite author and he loved reading his western novels. Before his Four Star Production Company went forth with this series, Powell got the rights to all of Zane Grey's work. This also might explain why you don't see any more work filming his stories.
But he found that some of the work was long and complex and not easily fit into a half hour or even an hour format. As a result other original material was commissioned. But at Powell's insistence always in the Zane Grey spirit.
For someone who liked Zane Grey Powell did few films that could be considered westerns. There were two musicals Cowboy From Brooklyn for Warner Brothers and Riding High for Paramount that had western settings. There was also the very good noir like western Station West for United Artists. That one is highly recommended for noir and western fans.
Powell's partners the other three stars Charles Boyer, David Niven, and Ida Lupino were more than content to just act occasionally in Four Star TV shows and reap the profits while Powell handled the business and creative end. Powell's motto was always like Madonna to reinvent himself from musical crooner to tough star of noir films to TV producer and tycoon. It was either that or go out of fashion very fast.
I think Powell succeeded in making a fine western anthology series that rivaled Death Valley Days for the years it was on, only ended by Dick Powell's death.
