Kerns' feature appearances have been infrequent, beginning with a small role in "Coma" (1978), and include the Martin Short vehicle "Cross My Heart" (1987), as Michael Ontkean's confused wife in "Street Justice" (1989) and as the artist aunt in "An American Summer" (1991). Mostly, Kerns has been a TV actor. She appeared in numerous episodics, including "Laverne & Shirley" and "Magnum, P.I.", and made her TV-movie debut in "The Million Dollar Rip-Off" (NBC, 1976). She went on to appear in both "Mother's Day on Waltons Mountain" and "A Wedding on Walton's Mountain" (both NBC 1982) and the miniseries "V" (NBC, 1983), before landing her first regular series role as Pat Devon, the stuntwoman girlfriend of real estate salesman Tony Roberts in the short-lived "The Four Seasons" (CBS, 1984). The next year, she was cast as Maggie Seaver, the mother who returns to journalism leaving her husband (Alan Thicke) to tend his psychiatric practice and their kids after school on "Growing Pains" (ABC, 1985-1992).

During the series' run, Kerns began churning out TV-movies, sometimes at a rate of two or three a year. Among some of the memorable ones were "The Preppie Murder" (ABC, 1989), as prosecutor Linda Fairstein; "Blind Faith" (NBC, 1990), as a murder victim; "The Big One: The Great Los Angeles Earthquake" (NBC, 1990), as a scientist braving the destroyed city to locate her daughter; "Shameful Secrets" (ABC, 1993), as a battered woman fighting for custody of her daughter; and "No One Could Protect Her" (ABC, 1996), as a woman hunting a serial rapist. Kerns often was involved in the development and production of these projects and, with a writing partner, occasionally wrote teleplays, including a 1989 episode of "Growing Pains" that was one of the highest-rated of the season.