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, The Rockford Files, Maverick, The Virginian, Alfred Hitchcock Presents, Wagon Train, Trackdown, Make Room for Daddy, Philip Marlowe, My Favorite Martian, Twilight Zone, Hazel, Kung Fu, Gunsmoke and Bewitched,Bonanza. She portrayed Jessie Copperton, a domineering cattle ranch matriarch, on Season 14; Episode 15 of Gunsmoke, entitled "The Twisted Heritage", in which her character has designs on welcoming Miss Kitty (Amanda Blake) into the family as a replacement for her former daughter-in-law. 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 (e.g., Adam-12, Emergency!). Gregg also played non-recurring character roles in four episodes of the long-running CBS series Perry Mason, including the 1958 episode, "The Case of the Cautious Coquette," and "The Case of the Pathetic Patient" from 1961.