She will play Gina, a trophy wife and mother of twin boys in the 10-episode limited series.
The project is inspired the Coen brothers’ film, yet will feature a new true crime story with new characters. Other stars currently signed on for the series are Sherlock‘s Martin Freeman, Colin Hanks (Dexter), and Billy Bob Tornton (Bad Santa).
Walsh, whose Private Practice character Dr. Addison Montgomery also appeared on six seasons of Grey’s Anatomy, can next be seen in the October 30th episode of DirecTV’s Full Circle.
FX’s adaptation of the film was given the greenlight back in March. It will be directed by Adam Bernstein of such hits as Breaking Bad and 30 Rock.
A premiere date has not yet been announced.