Despite appearing in a prestige film, Jaeckel went back to "B" action programmers in the late 50s, before landing supporting parts in bigger budget action films in the 60s, such as Robert Aldrich's "The Dirty Dozen' (1967). There were some exceptions, such as his turn as an American soldier accused of rape in a small town in post-war Germany in "A Town Without Pity" (1961) and as Paul Newman's lumberjack brother who, in a startling scene, drowns while caught under a log during high tide in "Sometimes a Great Notion" (1971). The latter earned Jaeckel an Oscar nomination for Best Supporting Actor. He followed with roles in Aldrich's "Ulzana's Raid" (1972) and Sam Peckinpah's "Pat Garrett and Billy the Kid" (1973) and a reteaming with Newman in "The Drowning Pool" (1975). Jaeckel was featured in Aldrich's "Twilight's Last Gleaming" (1977) and "All the Marbles" (1981) and was effective as the government agent tracking an alien (Jeff Bridges) in John Carpenter's "Starman" (1984). In the 90s, he was in such martial arts quickies as "The King of Kickboxers" (1990) and "Martial Outlaw" (1993).
Jaeckel began performing in TV anthology series such as "The U.S. Steel Hour" and "Playhouse 90" during the 1950s. In 1961, he joined the cast of "Frontier Circus" (CBS) as the advance man for a traveling troupe in the Old West. His series resume reads with a long list of action or crime series in which he co-starred, but which did not last long on the airwaves -- Lt. McNeil in "Banyon" (NBC, 1972-73), Hank Myers in "Firehouse" (ABC, 1974), Klinger in "Salvage I" (ABC, 1979), Master Chief Rivers in "Supercarrier" (ABC, 1988) and Lt. Quirk in "Spencer for Hire" (ABC, 1986-87). Jaeckel also co-starred on the ABC sitcom "At Ease" (1983), playing the by- the-book security boss, Major Hawkins, and he was the older, wiser figure in the first syndicated season of "Baywatch". His work in TV-movies has been somewhat more sporadic. He did a well- received turn opposite Linda Lavin in "The $5.20 an Hour Dream" (CBS, 1980) and returned to "The Dirty Dozen" for the franchise's TV movies in the mid-80s.