Before going into radio, Gregg played the double bass with the Pasadena Symphony and Pops. She was a member of the Singing Strings group heard initially on KHJ in Los Angeles in 1937 and later on CBS and Mutual.
Radio
Gregg was a prolific radio actress, heard on such programs as The Adventures of Sam Spade, Dragnet, Dr. Kildare, Gunsmoke, The Jack Benny Program, Let George Do It, Lux Radio Theatre, One Man's Family, Yours Truly, Johnny Dollar, The Screen Guild Theater, The CBS Radio Mystery Theatre, The Zero Hour, and Mutual Radio Theater. On the radio series Have Gun–Will Travel, Gregg portrayed Miss Wong, and also appeared in very different roles in the concurrent television series with Richard Boone. She had the role of Betty Barbour on One Man's Family and played Richard Diamond's girlfriend, the wealthy Helen Asher, on the radio series Richard Diamond, Private Detective. She later guest-starred in an episode of the television version of Richard Diamond, starring David Janssen. in Portland Expose
Feature films
Beginning with Body and Soul, Gregg made more than 45 films, including I'll Cry Tomorrow, Love Is a Many-Splendored Thing, Portland Exposé, The D.I., Operation Petticoat, All the Fine Young Cannibals, Man-Trap, House of Women, Spencer's Mountain, Two on a Guillotine, A Big Hand for the Little Lady, The Bubble, Madigan, Heaven with a Gun, Quarantined, A Walk in the Spring Rain, No Way Back, and S.O.B.
Television
Gregg once said of her work as a character actress on television: "I work steadily, but I have no identity." She added, "When casting people have a call for a woman who looks like the wrath of God, I'm notified." On television, Gregg appeared in nearly every narrative television series in the late '50s through the early 1970s, including Bourbon Street Beat, Hawaiian Eye, 77 Sunset Strip, Gunsmoke, Bonanza, The Lawman, Perry Mason, The Rockford Files, Maverick, The Virginian, Alfred Hitchcock Presents, Wagon Train, Mannix , Trackdown, Make Room for Daddy, Philip Marlowe, My Favorite Martian, Twilight Zone, Hazel, and Kung Fu.
Gregg may be best remembered for her many appearances in Dragnet. Jack Webb used her in dozens of roles on both the radio and TV versions of the show, as well as in the 1954 film version of Dragnet. In later years, she appeared on other shows produced by Webb's production company, Mark VII Limited ''.
Voice acting
Gregg was the voice for Riabouchinska, the ventriloquist doll in the 1956 Alfred Hitchcock Presents TV episode And So Died Riabouchinska. Gregg supplied the voice of "Mrs. Bates" in Psycho as did Jeanette Nolan and Paul Jasmin, all uncredited. Only Gregg did the voice in the sequels Psycho II and Psycho III. She voiced "Tarra" on the 1967 animated TV series The Herculoids. She reprised that role when the series was revived in 1981 as part of the Space Stars animated series.
Personal life
Gregg married producer Jaime del Valle in 1948. They had three children, Gregg, Jaime, and Ricardo. They were divorced on December 22, 1959. Gregg was active with Recording for the Blind, making recordings as a volunteer and serving on the group's board of directors.
