Oppewall entered the film industry in the late 1970s as a visual consultant to production designer Paul Sylbert on two Paul Schrader films, "Blue Collar" (1978) and "Hardcore" (1979). With "My Bodyguard" (1980), she began to work on set designs rising to production designer on "Tender Mercies" (1982), which recreated contemporary Texas. Oppewall went on to create designs for a number of fine films, notably the ranch settings for "Desert Hearts" (1985), Depression-era Albany in "Ironweed" (1987) and the contemporary middle-class milieu of "White Palace" (1990). For "School Ties" (1992), she re-created the rarefied world of a prep school in the 50s while "The Bridges of Madison County" (1995) required her to design an Iowa farmhouse and the famed bridges of the title. "L.A. Confidential" (1997) marked her most auspicious assignment to date. The meticulous design of 50s Hollywood, from its soundstages to a police station, from the mansion of a wealthy businessman to the poorhouses of minorities, earned her a richly deserved Oscar nomination. The following year, she received another Academy Award nod for her stellar work creating a 1950s TV sitcom world that gradually moves from black-and-white to color in "Pleasantville".