Parker was born in Fort William, Ontario. She was brought to southern California as a child by her mother, Mrs. Naudy Anna Parker. Her father was an English soldier. Parker graduated from the Convent of the Immaculate Heart in Hollywood in June 1931. At the time she resided with her parents, Mr. and Mrs. Thomas J. Parker, at 546 North Fuller Street in Los Angeles, California. Parker was selected from among a group of extras to attend the Fox Film studio training school for younger players.
Soon she was selected to play opposite George O'Brien in The Rainbow Trail (1932). The Rainbow Trail, written by Zane Grey, was the novelist's sequel to Riders of the Purple Sage. Parker starred with Tom Tyler and Carmelita Geraghty in a 1932-1933 movie serial produced by Universal Pictures entitled The Jungle Mystery. In July 1933, she was chosen to play the heroine in the Ken Maynard western, The Trail Drive (1933). That same year, she was John Wayne's leading lady in the first singing cowboy movie, Riders of Destiny.
After playing the sister of Greta Garbo in 1934's The Painted Veil, Parker signed a seven-year contract with Metro-Goldwyn-Mayer. The studio wanted a blonde who resembled Garbo as a young girl. Her new contract called for a starting salary of $75 a week and scales up to $1000 a week for the seventh year.
In November 1935, Parker purchased a new home in Beverly Hills, California. The following year she joined the ballet school of Dave Gould at MGM, along with Maureen O'Sullivan. By the fall of 1936, Parker was studying singing.
She played Marian Hardy in the extremely popular Andy Hardy movies in the late 1930s and early 1940s. She was in the original Hardy film, A Family Affair, in 1937, and though the subsequent films had a largely different cast, she remained. Mickey Rooney played the main character in the series, supported by such Hollywood pros as Lewis Stone, Ann Rutherford, and Fay Holden. The movies were directed by George "one take" Seitz. Out West with the Hardys (1938) features the entire Hardy family on a western trek to a large ranch. You're Only Young Once was the entry which revolved around Parker's romance with a married lifeguard on Catalina Island. Parker's character, Marion, appeared in most of the movies, and her romances were a recurring feature of the series.
It is rumored that she gave MGM some trouble at one point, because in 1941 she was "loaned" to ultra-low-rent studio Producers Releasing Corporation (one of the smaller production companies) for one picture, Gambling Daughters, a fate that usually befell actors who had displeased the higher-ups at the studios. All was apparently forgiven, though, as she made five more pictures at MGM before she retired in 1942.
Though she and the character she played were absent from the last two Andy Hardy films of the 1940s, Parker came out of retirement to play Marian Hardy in one more movie, in 1958. Andy Hardy Comes Home was an attempt to revive and update the series, but it was not a success. Parker then returned to the real estate business that she and her husband operated in Ventura, California, and she acted only very rarely afterward. She died in 1993.
Parker's sister, Linda, was an actress who appeared in a number of uncredited roles in the early 1930s. Both sisters once tested for the same part in David Copperfield. Parker was a close friend of actress Anne Shirley. During the mid-1930s the two kept a standing dinner date on Thursday nights.
In 1938 she married actor Robert Baldwin, who helped her to become a naturalized citizen in 1940. She died at age 79 on 25 July 1993, after what The New York Times called "a long illness". Her husband died in 1996.
She was survived by her husband Robert Sr., a daughter, Ann Bridges of San Diego; two sons, Robert Jr., of Tracy, California and John, of Ventura; five grandchildren and one great-grandchild.