text: Lenard guest-starred in several episodes of the original Mission: Impossible from 1966 to 1970, including one with Leonard Nimoy, and in a two-part episode of Buck Rogers in the 25th Century. He played the prosecutor in Fort Grant in the Clint Eastwood film Hang 'Em High (1968), and the hostile gorilla Urko in the television series Planet of the Apes. He made a guest appearance on Little House on the Prairie, in the episode "Journey in the Spring, Part I", playing Peter Ingalls, older brother of Charles Ingalls. He had roles in Gunsmoke several times, including the episode "Nowhere to Run" (1968).
  Lenard played a lead role in the film Noon Sunday, filmed on Guam with his costars Keye Luke; John Russell of the series Lawman; and character actor Stacy Harris. In The Radicals (1990), which recounted the beginnings of the Swiss Anabaptist movement in the 1520s, he played a composite historical character, Eberhard Hoffman, a Catholic bishop who serves as prosecutor in the trial of his former abbot Michael Sattler. In 1993, Lenard and fellow Star Trek actor Walter Koenig toured in a production of The Boys in Autumn. Lenard played a late middle-aged Huck Finn who re-encounters his childhood friend Tom Sawyer after a lifetime apart. Koenig played Sawyer.