Mary Jeanette Moran was born in Clinton, Iowa. The daughter of Louise Moran, a dancer with the famous Denishawn Dancers, and the celebrated artist Earl Moran, whose paintings graced many a barracks wall during World War II. One of Earl's favorite models was Norma Jean Baker, who later changed her name to Marilyn Monroe. Peggy never modeled for Earl, although a publicity still of the two of them was taken in Earl's atelier with Peggy posing.
From early childhood, she was called by the nickname, "Peggy". Peggy's mother took six-year-old Peggy to the office of Derio, a famous psychic of the time. Louise wanted her fortune told. Derio did not have the time for them but, when he came out of his office into the hall, he passed Peggy and her mother. Looking down at Peggy, he caressed her cheek, and said, "Hmm... an actress". From that moment on, Peggy knew she was destined to act.
Peggy appeared in some plays at school. She attended Hollywood High, where she was squired by Mike Stokey, founder of the original TV show, Stump the Stars (1947). She also attended John Marshall High for a time. There, she appeared in every play or show she could.
Hollywood soon beckoned. Peggy went to the front door of Warner Brothers and told the startled guard that she wanted to get into the lot because she was going to be a movie star. The guard introduced her to a producer who introduced her to an agent, and her career was started. She acted in a few clunkers at the beginning, playing mostly bit parts and minor roles. Among them was Ernst Lubitsch's masterpiece, Ninotchka (1939), in which Peggy appeared in two scenes as a cute cigarette girl. Later, when the picture was released, it appeared in Clinton, Iowa's only movie theatre under the marquee: "Clinton's Own Peggy Moran starring in Ninotchka (1939), with Greta Garbo". Peggy moved from Warner Brothers to Universal Pictures in the late 1930s. In between, she played the female lead in a Gene Autry western entitled Rhythm of the Saddle (1938). Working now at Universal, she met the producer, Joe Pasternak, who introduced her to his director, Henry Koster. It was love at first sight. Henry cast her first in a Deanna Durbin film, First Love (1939). She played Deanna's schoolmate. In the meantime, Universal was keeping Peggy busy starring in many of their "B" films. During this time, also, she starred in her most famous movie, the one for which she would always be remembered, The Mummy's Hand (1940). Even up to her passing, she received four or five fan letters a week from people who wanted photos of her from that film though it was produced over sixty years ago. Henry had discovered two comedians, Bud Abbott and Lou Costello, and their first movie, One Night in the Tropics (1940), starred Alan Young, Nancy Kelly, Robert Cummings, and Peggy Moran. Henry did not direct that one, or any other Abbott and Costello film, but he was responsible for their introduction to Hollywood, and Peggy was their first film character foil. Peggy was also tapped to star with Franchot Tone in Trail of the Vigilantes (1940), a Western that had all the other contract players from Universal, whether they were cowboys or not, including Broderick Crawford and Mischa Auer.
A year or so later, Henry and Peggy were married. Conrad Veidt was best man at the wedding in Las Vegas. Peggy was soon pregnant with her first son. Just after that, she was hired by Republic Pictures to play the female lead, opposite Roy Rogers, in King of the Cowboys (1943). Henry encouraged her to take the role even though she was pregnant. After that, whenever she saw the movie with her son, Nicolas Koster, she always told him, "You were there!".
That was Peggy's last film appearance except for some very recent films about stars of the early era. Peggy's life with Henry was the picture of marital bliss. They had two children, Nicolas Koster, who also acted in several of Henry's films, and Peter Koster, who works in Contra Costa County. Henry passed away in 1988. Peggy was quite active during these last fourteen years, playing billiards, dancing, entertaining, and traveling around the country to attend movie nostalgia conventions, where she invariably amazed and impressed everyone from hardened veterans of movies to new fans, with her wit, charm, intelligence and beauty. She was also active in her church, the Camarillo Church of Religious Science, where she studied to become a practitioner. On 26 August 2002, she was being driven from a friend's apartment in Ventura back to her apartment in Woodland Hills when the driver lost control of the car on the freeway. Peggy never recovered from the terrible damage that accident caused. She finally left us on 24 October, one day after her 84th birthday.