Dorothy Loudon’s performance as the evil orphanage administrator Miss Hannigan in Annie won her the Tony Award and the Drama Desk Award for Outstanding Featured Actress in a Musical in 1977. In the show she introduced the seminal showtunes “Little Girls” and “Easy Street.” Of her portrayal, Clive Barnes wrote, “As the wicked Miss Hannigan, Dorothy Loudon, eyes bulging with envy, face sagging with hatred, is deliciously and deliriously horrid. She never puts a sneer, a leer, or even a scream in the wrong place, and her singing has just the right brassy bounce to it.” Loudon later revisited the character of Miss Hannigan in the ill-fated 1990 sequel, Annie 2: Miss Hannigan’s Revenge, which closed quickly after a dismal pre-Broadway engagement in Washington D.C. In 1979, Michael Bennett cast Loudon as Bea Asher, a widow who becomes romantically involved with a mail carrier she meets at the local dance hall, in Ballroom. She was nominated for the Tony Award for Best Leading Actress in a Musical and the Drama Desk Award for Outstanding Actress in a Musical. She performed the number “Fifty Percent” from the musical during that year’s Tony Awards ceremony. During her rendition of George Gershwin’s “Vodka” at the 1983 Tony Awards ceremony while resplendent in a blue sequined gown, she ad-libbed “I’m too good for this room. I’m too good for this song…but I’m not too good for this dress!” At the 38th Annual Tony Awards ceremony in 1984, Loudon performed “Broadway Baby” from Follies. In The New York Times, John O’Connor said of her performance, “Miss Loudon has developed the art of mugging into something of a hyperactive disease.”

In 1980, Dorothy Loudon succeeded Angela Lansbury as Mrs. Lovett in Stephen Sondheim’s Sweeney Todd. In reviewing her performance for the Christian Science Monitor, David Sterritt said, “Her body sways like a reed in the emotional storms of her own scatter-brained creation, and her off-hand manner becomes still more off-handed when the most explosive matters are at stake … Loudon gives a comic characterization in the most classical tradition.” The following year she co-starred with Katharine Hepburn and Julia Barr in the play The West Side Waltz. In 1982 she won the Sarah Siddons Award for her work in Chicago theatre. She appeared in the 1983 Jerry Herman revue Jerry’s Girls and later the same year she played the role of the miserable middle-aged actress Dotty Otley on Broadway in Michael Frayn’s farce Noises Off. Dorothy Loudon was chosen as the replacement for Carol Burnett when Burnett left The Gary Moore Show in 1962. Although that collaboration was not altogether successful, the excellent reviews she received the same year for her Broadway debut in Nowhere to Go but Up proved prophetic. Coincidentally, the two roles Loudon later played so successfully on Broadway stage —Miss Hannigan and Dotty Otley — were both played by Burnett onscreen. She also was a frequent guest star on many New York based comedy and game shows. In 1979, Loudon starred in the television series Dorothy, in which she portrayed a former showgirl teaching music and drama at a boarding school for girls. It lasted only one season. She appeared in only two films, playing an agent in the film Garbo Talks (1984) and a Southern eccentric in Midnight in the Garden of Good and Evil (1997).

Dorothy Loudon was married to Norman Paris (born Norman Thaddeus Paris; 1925-1977), a composer who wrote the theme song for the television game show I’ve Got a Secret and arranged the music for Stephen Sondheim’s television musical Evening Primrose, from 1971 until his death in 1977. She had no children and never remarried. She died in New York City, aged 78, from cancer, and was interred in Kensico Cemetery in Westchester County, New York. She left no immediate survivors.