Leslie was cast opposite Sean McClory, as Jack McGivern, in The Californians, a fictional account of San Francisco during the California Gold Rush of the early 1850s. Richard Coogan starred in both seasons as Marshal Matthew Wayne. Other co-stars in the first season were Herbert Rudley as Sam Brennan and Adam Kennedy as newspaperman Dion Patrick. In the second season, Carole Mathews and Art Fleming, later the first host of the quiz program, Jeopardy!, joined the cast of the black-and-white half-hour series. Prior to The Californians, Leslie was known for her roles in three 1947 films The Woman on the Beach, with Robert Ryan and Joan Bennett, and two productions based on Zane Grey western novels with Tim Holt in the starring role: Under the Tonto Rim and Wild Horse Mesa. For a time she was engaged to marry Holt. Her acting career began with uncredited roles in twelve films, the first as Prudence in Under Western Skies (1945). Her first credited film role was as Jane Preston in the 1946 film Sunset Pass with co-star James Warren; the original Sunset Pass, a 1933 picture directed by Henry Hathaway, starred Kathleen Burke as Jane Preston, a young woman who seeks to rescue her brother from a life of crime. In March 1947, Leslie was among several actors and actresses attending the premieres in Kansas of Trail Street, an RKO Pictures release, with Randolph Scott in the role of Marshal Bat Masterson in the town of Liberal, Kansas. Leslie, however, is not listed in the credits as a cast member of the film.

Her first television guest-starring role came in 1949 on ABC’s The Lone Ranger; by 1955, she had made eight guest-starring appearances on the landmark western series. From 1950 to 1955, she appeared in four episodes of CBS’s The Gene Autry Show. Leslie was cast in two episodes of the NBC western series, The Roy Rogers Show; her first role being that of Bess Walton in “Jailbreak” (1951). Two years later, she was cast in the episode “Whirlwind Courtship” of the syndicated western anthology series, Death Valley Days, hosted by Stanley Andrews. In 1953, she also appeared as Jane Sawyer in “Arizona Troubleshooters” of another western series, Hopalong Cassidy. She was twice cast on the syndicated western series The Range Rider, as Joyce Lanyon in “Ambush in Coyote Canyon” (1952) and as Sue McCandles in “Saga of Silver Town” (1953). In 1954, she played Alias Annie in another syndicated western series, Annie Oakley, starring Gail Davis in a fictitious depiction of the markswoman Annie Oakley. She had met Davis c. 1945 at the RKO studios, and the two remained lifelong friends until Davis’ death in 1997.

From 1953 to 1955, Leslie was cast in five episodes each of two other syndicated western series, The Adventures of Kit Carson and The Cisco Kid. In 1956, she appeared in three episodes of the ABC western series, The Adventures of Rin Tin Tin, twice as Joan Lambert in “Wagon Train” and “Fort Adventure”. Her third role in that series was as Claire Corbin in “Rin Tin Tin and the Second Chance.” Leslie’s other western roles included the part of Peggy in “White Man’s Magic” (1957) of the ABC western series, Broken Arrow, as Nancy Barnett in “Three Graves” (1957) on Dick Powell’s Zane Grey Theater, and as Beth McGarrett in “The Legend” (1959) of Wanted: Dead or Alive, with Steve McQueen. She was cast twice in 1958 and 1959, respectively, on the Peter Graves NBC children’s western series, Fury, as Stella Lambert in “The Model Plane” and as Packy’s mother in “The Pulling Contest”. In 1959, she was also cast as Judy Travers in the episode “Treasure Trap” of another syndicated western series, Shotgun Slade, starring Scott Brady, and as Margaret Cook in “Day of Battle” of the NBC western series, Wichita Town, starring Joel McCrea.

Leslie also appeared in several drama series, including the 1954 role of Miss Oliver in the episode “High Stakes” of the series The Public Defender. In 1955, she appeared in “The Margaret Browning Story” of Don Fedderson’s CBS anthology drama series, The Millionaire. She appeared as Laura Mattley in “The Antidote” of the NBC Cold War drama, Behind Closed Doors. She appeared three times on the CBS police drama, The Lineup, starring Warner Anderson and Tom Tully, and twice on the NBC police series, M Squad, starring Lee Marvin. In 1957, she was cast as Muriel in “Death Defying Dozetti” of the series, Circus Boy. She portrayed a character Lydia in “Conscript” (1957) of the syndicated American Civil War drama series, The Gray Ghost, starring Tod Andrews as John Singleton Mosby. She played Barbara Lee Rickman in the 1957 episode, “The Fishing Trip” of the syndicated police drama, Code 3. In 1958, Leslie played Myrna O’Malley in “Short Haul” on the CBS crime drama, Richard Diamond, Private Detective, starring David Janssen. In this episode she was cast as the wife of Ted O’Malley, played by Sean McClory, Leslie’s co-star from The Californians.

By 1960, Leslie’s career began to wind down. She was cast twice on CBS’s Lassie. In 1960, she played Amy Carson in “The Quick Noose” of the NBC western series, Riverboat, starring Darren McGavin. She played Midge Lewis in the 1960 episode, “The Big Blackout”, of the NBC mystery series, Thriller, hosted by Boris Karloff. In 1961, she appeared as Jean Telford in “Flee Now, Pay Later” of Rod Cameron’s syndicated detective series, Coronado 9, and as Josie in “Gladys Goes to College” on the CBS sitcom, Pete and Gladys, starring Harry Morgan and Cara Williams. He portrayed Beth Thomas in the 1961 episode “The Female Artillery” of The Tall Man. She appeared twice each on CBS’s The Jack Benny Program and Perry Mason, starring Raymond Burr. In 1964, she was cast as Evelyn Waltham in “The Leper” episode of the Christian series, This Is the Life. Leslie played Ada Mayberry in the 1966 episode “Seminole Territory” on NBC’s Daniel Boone, starring Fess Parker in the title role. Her last acting role was as Dorothy Vetry in the 1968 science fiction film, The Bamboo Saucer, starring Dan Duryea and John Ericson. Leslie was twice married; her husbands were socialite Charles Pawley (1915-1975), to whom she was wed from 1949 until c. 1960, and Albert Jason Coppage (1920-1990), who was her spouse from 1968 until his death in San Juan Capistrano. She spent her later years in Mission Viejo, California. She died in 2000 of pneumonia at the age of seventy-four in San Juan Capistrano, south of Los Angeles.