After six years in the Texas State Legislature, Leland was elected to the United States House of Representatives in November 1978 to represent Texas's 18th District and was re-elected easily in 1980, 1982, 1984, 1986 and again in 1988 to six two-year terms, serving until his death. The congressional district included the neighborhood where he had grown up, and he was recognized as a knowledgeable advocate for health, children and the elderly. His leadership abilities were immediately noticed in Washington, and he was named to serve as Freshman Majority Whip in his first term, and later served twice as At-Large Majority Whip. Leland was re-elected to each succeeding Congress until his death.