Prior to Yellowstone, Reilly took on many roles in television, usually a one-off appearence in a TV series. These series included: Prime Suspect 4: Inner Circles, The Biz, Wonderful You, The Ruth Rendell Mysteries, Peak Practice, Agatha Christie: Poirot, He Knew He Was Right, Joe's Palace, A for Andromeda, Above Suspicion, Black Box

Reilly gained widespread critical acclaim and popularity for her role as Beth Dutton in the Paramount Network series 'Yellowstone'. Her performance as the fierce and complex Beth has been a highlight of the show and has significantly boosted her career.