Born Charlotte Gercke in New York City, she was the daughter of journalist George Gercke and astrology practitioner Ruth Hale Oliver, who divorced when Charlotte was still a child. At the end of World War II, George Gercke joined the United States Information Agency and in early 1946 was posted to Japan as a supervisor overseeing news dissemination and instruction in democratic institutions during the U.S. occupation. Charlotte studied at the Tokyo International College from 1949 to 1951 and developed a lifelong interest in Japanese society and its absorption of American pop culture. In 1977, twenty six years after her early experiences in Japan, she wrote and directed Cowboysan, a short film which presents the fantasy scenario of a Japanese actor and actress playing leads in an American western. Following her return from Japan in 1951, Charlotte joined her mother in California, where Ruth Hale Oliver eventually became a well-known Hollywood astrologer.

At the age of twenty, Charlotte went back to the East Coast to begin drama studies at Pennsylvania's Swarthmore College followed by professional training at the Neighborhood Playhouse in New York City. After working in summer stock, she adopted the stage name "Susan Oliver" and first appeared on television playing a supporting role in the July 31, 1955 episode of the live drama series Goodyear TV Playhouse, followed by parts in other Golden Age of TV shows.

1957 was a banner year for Susan, including Broadway, numerous TV shows and a starring role in a movie. She began the year with a major ingenue role in her first Broadway play Small War on Murray Hill, a Robert E. Sherwood comedy about the intrigues surrounding General Howe's (Leo Genn) visit to New York in 1776, at the start of the Revolutionary War. It opened at the Ethel Barrymore Theatre on January 3, 1957 and played 12 performances, closing on January 12. The short run was a disappointment, but it was immediately followed by meaty roles in live TV dramas on Kaiser Aluminum Hour, The United States Steel Hour and Matinee Theater. She then went to Hollywood, where she appeared on Climax!, one of the few live drama series based on the West Coast, as well as in a number of filmed shows, including the October 30, 1957 episode of Wagon Train and a memorable installment of Father Knows Best (broadcast on March 5, 1958), in which she was the Anderson Family's titular Country Cousin. She also won the title role in her first motion picture The Green-Eyed Blonde, a low-budget independent melodrama released by Warner Brothers on the bottom half of a double bill. The film was scripted by renowned blacklisted writer Dalton Trumbo using the name of a "front". Despite the alluring title and exploitative publicity stills designed to capitalize on Susan's attractiveness, the storyline was raw social protest mixed with soap opera, portraying outcast teenage girls in reform school, banding together to secretly shelter one of the girls' baby. Susan played the tough veteran inmate considered the unofficial leader of the group. The downbeat ending had the baby being discovered and removed, followed by a riot which resulted in the death of Susan's character. Ironically, The Green-Eyed Blonde would turn out to be the only motion picture on which Susan Oliver received first billing. At the end of the year, Susan returned to New York, appearing in the December 12, 1957 broadcast of the prestigious live drama series Playhouse 90. Her performance in the John Frankenheimer-directed teleplay was well-received and she returned to Playhouse 90 two more times, March 26, 1959 and January 21, 1960.

In 1958 Susan was back in the Golden Age of TV Drama, acting on Kraft Television Theatre and Suspicion, as well as rehearsing for a co-starring role in a Broadway play. Patate (which in French means "spud", but can also mean "chump") was a comedy by Marcel Achard adapted for American audiences by Irwin Shaw. Susan's leading men were veterans Tom Ewell (in the title role) and Lee Bowman. Patate opened at Henry Miller's Theatre on October 28, 1958 and closed on November 1, its 7-performance run being even shorter than that of her first show, Small War on Murray Hill. Nevertheless, Patate won Susan a Theatre World Award for outstanding "breakout" performance. It also turned out to be her final Broadway appearance.

Noted for her striking good looks, the blonde actress spent the remainder of her career in Hollywood, going on to play in more than one hundred different television shows and made-for-TV movies. She appeared in the notable 1960 motion picture BUtterfield 8 and in 1964 had a co-starring role opposite George Hamilton in Your Cheatin' Heart in which she played Audrey Williams, wife of country music legend Hank Williams. She was also in Jerry Lewis' wild slapstick vehicle The Disorderly Orderly. The Frank Tashlin-directed film cast her in an oddly serious role as a beautiful former cheerleader from Jerry's high school days, who after having been used and exploited by men, attempted suicide and wound up in the medical instutitution where Jerry is the titular character. Jerry has never gotten over his lovesickness for her, and finding out that she is destitute, works overtime to pay for her stay. Unaware of this fact, she rejects him as an apparent peeping tom, when in his fumbling eagerness to please her, he manages to fall under her hospital bed. As a basically unsympathetic, neurotic and ultimately pitiable character, Susan brought a note of pathos to the otherwise knockabout comedy, but to some critics, seemed jarringly out of place with the rest of the proceedings.

On Star Trek Susan had her most iconic role as "Vina", the lone survivor of a spaceship crash landing on Talos IV, and Captain Christopher Pike's love interest in the first pilot The Cage (1964, televised in re-edited form 1966). It is also Susan who is seen in the end credit images of early episodes of TOS as the green-skinned Orion Slave Girl.