Burke graduated from Colonial High School in 1974, and won the senior superlative “Most Likely to Succeed.” In 1972, she won the Miss Flame crown from the Orlando Fire Department and went on to become State Miss Flame. In her senior year of high school, she won the Miss Florida title for 1974; she was the youngest Miss Florida titleholder in pageant history. Burke won a talent scholarship from the Miss America Organization, allowing her to attend a two-year study program at the London Academy of Music and Dramatic Art.

In 1974, as part of winning Miss Florida, Burke appeared on the ABC-TV show Bozo the Clown, filmed in Orlando, Florida. She worked as the magical assistant to Herbert L. Becker. The two worked together for six months.

In 1980, Burke portrayed the role of the second Bonnie Sue Chisholm in the CBS western miniseries, The Chisholms. Her best-known role as Suzanne Sugarbaker in Designing Women was created by Linda Bloodworth-Thomason. Before Designing Women, Burke spent a year on Filthy Rich in 1982 playing the wily young widow, Kathleen Beck. After that, she played female football team owner Diane Barrow on 1st & Ten.

Since the early 1990s, Burke’s weight has been a subject of discussion in the tabloid press. Her struggles with weight, depression, and eating disorders stretch back to her pageant days in the early 1970s. She became a much-parodied figure in the press due to the media’s incessant obsession with her weight, including in a skit on Saturday Night Live, wherein Leon Phelps from The Ladies Man has a sexual fixation with her. In 1989, Burke asked Thomason to write an episode addressing her weight. The episode, “They Shoot Fat Women, Don’t They?”, had Suzanne Sugarbaker going to her 15-year high school reunion and having her feelings hurt after hearing disparaging remarks about her weight. Her performance on this episode is said to have led to her receiving her first Emmy nomination as Best Actress. She earned a second nomination the following year.

Burke earned two consecutive nominations for the Primetime Emmy Award for Outstanding Lead Actress in a Comedy Series in 1990 and 1991, the only lead female cast member of Designing Women to do so. Alice Ghostley received a nomination for Supporting Actress in a Comedy in 1992, for her recurring role as Bernice Clifton. Meshach Taylor received one in 1989 for Supporting Actor in a Comedy Series. In 1990, Burke publicly expressed dissatisfaction with the show on a televised interview with Barbara Walters and other media outlets. She argued on Entertainment Tonight that there was a labor dispute, and actors were often forced to work over 15 hours per day, with executives even blocking the doors and keeping actors on set. She also said that castmate Dixie Carter, who had once been her close friend and maid of honor at her wedding to Gerald McRaney, was not speaking to her as she sided with her bosses. At the end of the fifth season of Designing Women in 1991, Burke was let go from her contract due to her contentious relations with Carter and the Thomasons.

Burke became a blonde for the short-lived sitcom Delta (1992), in which she portrayed an aspiring country music singer. When ratings plummeted, Burke became a brunette again. In 1995, she and Linda Bloodworth Thomason reconciled their differences, and Burke returned as Suzanne Sugarbaker in Women of the House (1995), but that show also met an early demise.

In 2002, she reunited onscreen with Carter in a guest appearance on Carter’s series Family Law.

Burke made her Broadway debut in September 2003, when she starred as Mrs. Meers in the musical Thoroughly Modern Millie. She was the third actress to play the role in the production, after Harriet Harris and Terry Burrell. She played the role until February 2004, before being succeeded by her Designing Women co-star Dixie Carter. Burke then played the role of Truvy in the original Broadway production of Steel Magnolias, playing the role for the shows entire four-month run from April 4 – July 31, 2005.

Burke is a supporter of gay rights, and has worked with openly gay playwright and screenwriter Del Shores on many occasions, in Sordid Lives and Southern Baptist Sissies. In 2006, Burke and openly gay Tennessean actor Leslie Jordan were uninvited from the Nashville talk show Talk of the Town after the show’s managing director decided the subject matter to be discussed would offend the conservative viewers. Burke first became supportive of gay people and gay rights through attending acting school in London and also through her sister, Jennifer, who is a lesbian.

In March 2012, it was announced Burke had been cast in the ABC comedy pilot Counter Culture. However, after Burke fell on the set, production of the pilot was suspended and it was not picked up to series.