Hillary Brooke's image as the epitome of glacial, regal, upper-class British gentility is muted somewhat by the fact that she was born Beatrice Sofia Mathilda Peterson to a middle-class American family in Long Island, New York. She was the sister of actor Arthur Peterson, best-known as the demented "Major" on the soap-opera satire Soap (1977). Always a beauty, she had a successful career as a photographer's model before breaking into show business. Her "British" accent came about when she realized that she was just one of innumerable tall, good-looking blondes vying for roles, and needed something to make her stand out among them. She came up with affecting a British accent and it worked; she began to get more and more roles that called for a "British" blonde, so she kept the accent.

Her film debut was in New Faces of 1937 (1937), in which -- billed as "Beatrice Schute" -- she played a showgirl. She began working steadily in films in the early 1940s, and appeared in such major productions as The Woman in Green (1945), The Fuller Brush Man (1948), The Philadelphia Story (1940), Dr. Jekyll and Mr. Hyde (1941), Wake Island (1942), Jane Eyre (1943) and The Enchanted Cottage (1945), in addition to the usual run of "B" westerns and thrillers in which many up-and-coming young actresses had to put in time. In the early 1950s she began appearing on television including 23 appearances on The Abbott and Costello Show (1952) as "Hillary Brooke", the object of Lou Costello's affections. She had worked previously with the duo in their second color film, Abbott and Costello Meet Captain Kidd (1952), in which she played a pirate chief.

She had no compunctions about taking a pie in the face, a vase on the head, a pratfall, or tussling with Bingo the chimp, and more than held her own. She also had a similar role as the girlfriend of Vern Albright (Charles Farrell) in My Little Margie (1952) and alternated between television and film roles in the 1950s. One of her better-known roles was as little David MacLean (Jimmy Hunt)'s mother, Mary, who is taken over by the Martians in the sci-fi classic Invaders from Mars (1953). She also played Doris Day's character's best friend in The Man Who Knew Too Much (1956), and, the next year, had her final film role in Spoilers of the Forest (1957), after which she turned exclusively to television.

She retired from the film industry in 1960, after marrying film executive Raymond A. Klune, and died in Bonsall, California, aged 84, in 1999.