In 1959, Patrick Kelly called Fuller to his office to offer him an opportunity to co-star opposite Academy Award-winner Ray Milland, in the CBS detective series, "Markham." Fuller quickly turned down the role because he wanted to appear in westerns. He was David Dortort's second choice for the role of Lorne Greene's youngest cocky, impish son, Joseph "Little Joe" Cartwright, on NBC's "Bonanza," but he lost the role to another young and then unknown actor--Michael Landon, whose career was made by that role. At about the same time, Fuller landed the co-starring role of Jess Harper on "Laramie," which ran from 1959 to 1963, and Fuller was cast opposite another of his best friends, John Smith. Being the unknown, struggling actor that he was, Fuller was asked to do a screen test for the character of Slim Sherman, and John Smith had originally been cast as Jess Harper. Fuller insisted that he would be better cast as Harper, and after the screen test, he won the role of Jess, while Smith got the part of Slim.