Welch had one of her finest hours displaying her comic timing as Constance in Richard Lester's version of the "The Three Musketeers" (1973), winning a Golden Globe for her efforts. She appeared again as Constance in Lester's follow-up "The Four Musketeers" (1975) and shone as the Jugs of Peter Yates' "Mother, Jugs, and Speed" (1976), the easygoing camaraderie of the three principles (with Bill Cosby and Harvey Keitel) providing a refreshingly strong role for her. Hollywood, however, cast her body more than anything (she was a sex symbol after all) and refused to see an actress of any depth. In order to branch out into more dramatic fare, Welch moved to the small screen during the 80s earning plaudits for her work in NBC TV-movies like "The Legend of Walks Far Woman" (1982), "Right to Die" (1987, in which she was convincing as a woman stricken with Lou Gehrig's disease) and "Scandal in a Small Town" (1988).

Welch sued MGM in 1980 for firing her from "Cannery Row" (1982), eventually pocketing $14 million. In 1981, she made her Broadway debut succeeding Lauren Bacall in "Woman of the Year" and upped her credibility immensely. She made her series debut as a regular in the revamped version of Darren Star's "CPW" (CBS, 1996) before replacing Julie Andrews on the Great White Way the following year in "Victor/Victoria". Perhaps it strained credulity (not to mention challenging costumers) to present her as a woman passing for a man, but her presence could not keep the show from closing. Despite the setback, Welch has remained committed to developing her craft, appeared onstage in a revival of George Bernard Shaw's "The Millionairess" in 1998 (having previously played the role in a British tour). She also returned to features that year playing Grace Kosik the nemesis of comedian Carrot Top in the uneven comedy "Chairman of the Board".