Bromfield was a regular performer on the 1974 The Bobbie Gentry Show.
She performed stand up comedy on the first episode of Saturday Night Live on October 11, 1975. After being introduced by Don Pardo, her monologue begins:
I don't look like a comedian, do I? (starts talking rapidly like a strict school teacher) That's because I'm not, I'm a school teacher, and I'm going to need a lot of silence in this room if I'm going to talk. (claps three times) People people people, please please, people people, am I in a zoo?! All right people, let's bring you out of the suburbs and into the city. I'd like to have a few words with you. (casually bites her pinky finger nail) Okay, okay, people...now...today we have a big volleyball game ahead of us, people, and as you know the principal is counting on us winning the cup.
She also appeared on another SNL episode in 1978.
In 1979 she played "Mary Mary" on the ABC series Angie. In 1980, she appeared as the character of "Debbie Smith" on The David Letterman Show. She played "Laney Gibbs" on two episodes of Best of the West in 1981 and appeared on six episodes of SCTV between 1983-1984. In 1984, she appeared on four episodes of The New Show, another NBC sketch comedy show produced by Saturday Night Live creator Lorne Michaels.
In 1993, she appeared as herself on Friends of Gilda. As the character "Faith Burdette", Bromfield appeared on nineteen episodes of Grace Under Fire between 1993 and 1995. In 1995, she appeared on Joe Bob's Drive-In Theater.
Bromfield has also appeared on shows broadcast in Canada only such as the CBC show 90 Minutes Live on the BCTV show Zig Zag.
Her movie credits include the role of "Doris" in the 1983 movie Mr. Mom, the role of "Belle Haimes" in the 1987 movie Home Is Where the Hart Is, the role of "Detective Casey" in the 1989 movie Who's Harry Crumb?, the role of "Miss Purdah" in the 1991 movie 'Nothing But Trouble, the role of "Brandy" in the 1992 movie Caged Fear, and the role of Dawny in the 1992 movie This Is My Life. In the 1993 movie Needful Things, her character "Wilma Jerzyck" is hit in the face with a meat cleaver by the character played by Amanda Plummer.
As a voice actor, she made her animation debut in the 1974 television movie The Gift of Winter. A Halloween-themed sequel four years later that was titled Witch's Night Out. Bromfield was the voice of "Honey Bunny Funnybunny" on an ABC Weekend Special in 1994 based on the works of Marilyn Sadler. She voiced "Nurse Molly" on the Camp Candy cartoon show and has provided voices for Popples, Animaniacs, Tiny Toon Adventures, Superman: The Animated Series and other animated shows.
In 1998, Bromfield was credited as a supervising producer on The Kids in the Hall. She is also credited as a writer on a number of shows in which she has appeared and other television shows such as That Thing on ABC (1978) and Space Cases (1996).
Her sister, Lois Bromfield, is also a comedic actor, writer, and producer with a long list of credits.
