As the daughter of successful actors Christine Baranski and Matthew Cowles, Lily Cowles largely kept out of the spotlight. Cowles graduated from Princeton before turning to acting. Her first significant role came in the political satire "BrainDead" (CBS, 2016). She played a recurring role in the show, which starred Mary Elizabeth Winstead as a documentary filmmaker who realizes that aliens have infected members of Congress.
In 2019, Cowles co-starred in "Roswell, New Mexico" (The CW, 2019-), a reboot of the fan favorite "Roswell" (The WB, 1999-2001, UPN, 2001-02).