According to the commentary on the DVD for Back to the Future Part III, Steenburgen's children were fans of Back to the Future and she readily accepted when cast for the role of Clara.
Steenburgen's film debut was in the 1978 Western/comedy Goin' South, which starred Jack Nicholson and Christopher Lloyd. She starred with Lloyd again in the 2002 movie Wish You Were Dead.
Back to the Future Part III was Steenburgen's second time-travel movie. In the 1979 movie Time After Time, she played the role of Amy Robbins, a 20th century woman who falls in love with a visitor from the 19th century (Malcolm McDowell as H.G. Wells).