Born on March 9, 1953, in Boston, Massachusetts, Koslow was raised with a strong love for colonial life alongside her sister, Linda, and brother, Donald, due to her mother's role as a docent. She was educated at the University of Massachusetts Amherst and Virginia Polytechnic Institute & State University, graduating with a degree in theatre and costume design.
Koslow began her career as a costume designer for a summer stock theater group in Virginia, where she was also asked to audition for the role of Vera in the play "Ten Little Indians." She eventually put her costume designing skills aside to focus on acting, appearing in regional productions such as "Cat on a Hot Tin Roof" and "Dial M for Murder."
Koslow then moved to Los Angeles to pursue a television career, landing various guest roles before securing the role of the scheming Lindsay Wells on the hit CBS soap opera The Young and the Restless in 1984, a character she portrayed until 1986.
The serial's creators, William J. Bell and his wife Lee Phillip Bell, then asked Koslow to become an original cast member on their new sister soap, The Bold and the Beautiful, which debuted in the spring of 1987. She portrayed Eric Forrester's design assistant, Margo Lynley, from the serial's inception until 1992, when she left to start a family.
Throughout the early 1990s, Koslow continued to work in television, appearing in guest roles on series such as Silk Stalkings and The Nanny. However, she was eventually lured back to daytime television in 1996 to replace actress Deborah Adair on the NBC soap Days of Our Lives.
In the role of Kate Roberts, a vindictive call girl turned corporate executive, Koslow flourished on Days of Our Lives, quickly becoming a character fans loved to hate. Her character was known for her wickedness and deception, particularly her ongoing feud with fellow Salem resident Sami Brady and her tumultuous marriage to mogul Victor Kiriakis.
In contrast to her on-screen persona, Koslow has been married to make-up artist Nicky Schillace since 1987 and resides on a ranch in Northridge, California, with their two children and various animals.
