She appeared on many of the iconic programs of the 1950s and 1960s. She did two episodes of "Lassie", "Lassie and the Swamp Girl" and "Little Dog Lost" as "Mattie" in the mid 60's. She followed that up with appearances on "Gunsmoke" and other iconic shows. At the age of 15, after appearing in "Yours, Mine and Ours" with Lucille Ball, her childhood career came to an end and she concentrated on getting her education at Cleveland High School in Reseda, California.

Cupito began her career as a child Actress at age five in a 1957 episode of the CBS television network anthology series Playhouse 90. In January 1960, she displayed her talent as a ballet Dancer on The Dinah Shore Chevy Show. Three months later, she followed that up with her first of three Twilight Zone episodes, uncredited as a little girl in "Nightmare as a Child", Sissy Johnson in the fourth-season episode, "Valley of the Shadow", and Susan in the fifth-season episode, "Caesar and Me". She appeared in an episode of My Three Sons as Melinda, the daughter of a busy divorced woman. In 1960, she also appeared in the third season of Sea Hunt, as the girl trapped in a mine cave-in in the episode "Cindy".

She was featured in the musical film Gypsy (1962), as Baby June. She appeared uncredited in the birthday party and school house scenes in the thriller film The Birds (1963). In 1963, she played the role of Winter Night in the episode "Incident of the Hostages" on CBS's Rawhide. In 1964, she starred as a blind girl called Minerva Gordon in a two-part episode of The Outer Limits entitled "The Inheritors" with Robert Duvall, and appeared in the Western film Stage to Thunder Rock.

She appeared in the final episode of the Western series Branded in 1966, playing the role of an orphaned girl named "Kellie" in an episode of the same name. She was part of the ensemble cast in the film Yours, Mine and Ours (1968), which starred Lucille Ball and Henry Fonda. Cupito was also in the season 8, episode 1 of The Andy Griffith Show titled "Opie's First Love" as Mary Alice.

At age 18, Cupito changed her name to Morgan Brittany and then appeared with Gene Kelly in his Las Vegas show, Gene Kelly's Wonderful World of Girls, as a Dancer. She then moved to New York City, where she modeled for The Ford Modeling Agency, and appeared in several TV commercials and print ads (including a three-year stint as "The Ultra Brite Toothpaste Girl"), and was spokesmodel for brands such as L'Oreal,(Maybelline) Ford, Levi's and Camay. In December 1972, she played 'Cynthia', a childhood friend of Bridget, (Meredith Baxter), in episode 12, "The Homecoming" on the series Bridget Loves Bernie. In 1974, she was hired by the Japanese cosmetics company Kanebo to be the "face" of their product "Ireine", and so moved to Tokyo from 1974-1976 and traveled around the world as the image of "Kanebo Cosmetics". In 1976, she returned to the United States and restarted her acting career.

In 1976, Brittany portrayed Vivien Leigh in the biography Gable and Lombard, the first of three occasions on which she would play the famous Actress. She had also done a cameo appearance in the John Schlessinger film "The Day of the Locust" as Leigh in the huge mob sequence at the climax of the film. That was followed by television movies and television series, such as The Amazing Howard Hughes (1977), "(Delta County USA)" The Initiation of Sarah (1978), Death Car on the Freeway (1979), The Dream Merchants (1980) and LBJ: The Early Years (1987). She starred in a television pilot, Stunt Seven (aka The Fantastic Seven), in 1979 with Christopher Lloyd, Patrick MacNee, and Elke Sommer. In 1980, while filming an episode of The Dukes of Hazzard, Brittany met her Future husband, stuntman Jack Gill.

During the 1980s, Brittany was a national ambassador for the March of Dimes. She traveled the United States raising funds and bringing awareness to the prevention of birth defects. She participated in the Congressional "Walk" in Washington, D.C., with such members of the House of Representatives as Speaker Tip O'Neill. Her time with the March of Dimes lasted two decades, and during her involvement she was invited to the White House in 1986 with Ronald Reagan and again with Bill Clinton. Brittany splits her time between southern California and Atlanta, Georgia.

Brittany married stuntman Jack Gill in 1981. They are the parents of Actress Katie Gill and musician/stuntman Cody Gill.

In 1984, Brittany co-starred in the short-lived ABC drama series, Glitter, as Kate Simpson, a reporter for an entertainment magazine. This was one of several collaborations with Producer Aaron Spelling throughout her career. Her first show with him had been an appearance in Burke's Law, in 1964 when Brittany was a child. Later, as an adult, she appeared in seven episodes of The Love Boat, Hotel, Fantasy Island, Melrose Place, and the 1990s revival of Burke's Law. She appeared in The Wild Women of Chastity Gulch, which starred Joan Collins.

Brittany and Bruce Jenner hosted a Sports show Star Games. She later hosted over 100 episodes of the magazine show Photoplay, produced by Jack Haley Jr. She has guest starred on other series, including Married... with Children, Murder, She Wrote "(Perry Mason Mysteries)", (Dear John), (Sabrina the Teenage Witch) and The Nanny. In film, Brittany starred in Sundown: The Vampire in Retreat (1989).

In the 1990s, Brittany appeared in the independent films, including Riders in the Storm (1995), Legend of the Spirit Dog (1997), The Protector (1998), The Biggest Fan (2002), Mothers and Daughters (2006) and Americanizing Shelley (2007). She also appeared in the docudrama, 1 a Minute (2010), and made a guest appearance on the television series Sabrina, the Teenage Witch and Son of the Beach.

Morgan also spent time on the Home Shopping Network selling her line of Victorian porcelain dolls. The Morgan Brittany Collectable Doll collection sold over a million dollars worth of merchandise in a short period of time in the late 90's. She then became the spokesperson for the Gale Hayman Cosmetics line which also was sold on HSN in the early 2000s. The skin care/cosmetic line was also highly successful. She also started her own line of children's clothing in the 90's called "Stunt Gear For Kids". It was sold in high-end boutiques as well as Nordstrom stores.

Her first book, along with co-authors Ann-Marie Murrell and Dr. Gina Loudon, What Women Really Want, was released September 2, 2014. She is a recurring guest on Hannity (FOX News), The Rick Amato Show (One America) and has appeared on The Kudlow Report (CNBC), "Fox and Friends", "The Dennis Miller Show" and "Huckabee". Brittany is a co-owner and anchor for PolitiChicks, an online news site with a conservative perspective. Her second book with co-author Ann-Marie Murrell was released in 2017. "PolitiChicks: A Clarion Call to Political Activism" is a compilation book of essays from "PolitiChicks" Writers. Morgan now travels the country speaking at major venues like "The Heritage Foundation", and other conservative organizations. She, Murrell and Sonya Sasser are in demand as speakers at major conservative political events all around the country.