She moved to CBS-affiliate WTOP (now WUSA) in Washington, D.C., in 1976. Two years later, Mitchell moved to NBC's network news operation, where she served as a general correspondent. In 1979, she was named the NBC News energy correspondent and reported on the late-1970s energy crisis and the Three Mile Island nuclear accident. Mitchell also covered the White House from 1981 until becoming chief congressional correspondent in 1988.