"[6] Over the next four decades, she appeared in a number of Broadway productions, including Goodbye, My Fancy (1948), The Time of the Cuckoo (1952), Inherit the Wind (1955), Catch Me If You Can (1965), and Long Day's Journey Into Night (1986).

She departed the show after two months to appear with Helen Hayes in the play The Wisteria Trees, adapted from Anton Chekhov's The Cherry Orchard, by Joshua Logan.

She guest-starred in many western television series, including The Texan,[9] Mackenzie's Raiders (as Lucinda Cabot in "The Lucinda Cabot Affair"), The Man from Blackhawk, Riverboat, Wanted: Dead or Alive (episode "Secret Ballot"), Trackdown, Bat Masterson, The Rifleman, The High Chaparral , Gunsmoke, Maverick, Pony Express, Stagecoach West, Bonanza, The Wild Wild West, Have Gun - Will Travel (where she played a Chinese woman), and Wagon Train.

[citation needed] Her other credits were on drama series, such as Alfred Hitchcock Presents; Richard Diamond, Private Detective and The Fugitive, both starring David Janssen; The Eleventh Hour; The Lloyd Bridges Show; Mannix; Route 66 (episodes "The Layout at Glen Canyon" and "City of Wheels"); Straightaway; Bus Stop; Target: The Corruptors!

[11] Her feature film credits include A Rage to Live (1965); The Molly Maguires (1970), with Sean Connery; Dr. Cook's Garden (1971); Old Boyfriends (1979); Ironweed (1987); Message in a Bottle (1999); and Uninvited (1999).

Leslie was a regular on NBC's The Richard Boone Show, which garnered her an Emmy Award nomination for Outstanding Single Performance by an Actress in a Leading Role for her work in the episode "Statement of Fact.

[12] Leslie's 1986 Broadway portrayal of a drug-addicted mother in Long Day's Journey into Night brought her a Tony Award nomination for Best Featured Actress.