Ernest K. Lindley, 79, a noted Washington correspondent for many years and then an official of the State Department, died Saturday at Sibley Memorial Hospital. He had cancer.

Mr. Lindley was in the vanguard of the wave of journalists attracted to Washington to cover the New Deal of President Franklin D. Rossevelt. He had covered Roosevelt when he was governor of New York for the old New York Herald Tribune and the newspaper sent him here when Roosevelt was elected President.

He soon established a reputatiion among his colleagues and members of Congress and the administration as the leading authority in the press corps on Rossevelt and his policies. He was the author of several books on the subject.

In 1937, Mr. Lindley left The Herald Tribune to become the Washington bureau chief of Newsweek magazne, which was organized that year. A year later, he joined The Washington Post as a reporter and columinist. He was hired by Eugene L. Meyer, then the publisher of the newspaper, because of his expertise on the New Deal. Mr. Lindley remained on The Post until 1943 and on Newsweek until 1961.

He then became a special assistant to Secretary of State Dean Rusk and a member of the State Department's Policy Planning Council. He remained at State until 1969, when he received the department's Superior Service Award.

In his years with Newsweek, Mr. Lindley wrote a weekly column, "Washington Tides," in addition to running the bureau. His daily columns for The Post were syndicated.

He found time, too, to work as a commentator on network radio and, later television programs and to write for various national magaznes other than Newsweek and for encyclopedias. He traveled widely for Newsweek and was a frequent lecturer on international affairs at the National War College and elsewhere.

During World War Ii, Mr. Lindley organized a group of veteran reporters that met frequently with Gen. George C. Marshall, the Army chief of staff, and Administrator Ernest J. King, the chief of naval operations, and other high officials for briefings on sensitive military and diplomatic matters.

The famous "Lindley rule," which still is invoked at times by officials in their dealings with the press, was much used in those encounters. Under the rule, information gleaned from officials may be published, but without attribution to any source. Reporters often use such vague attributions as "government officials" or "unimpeachable sources" to lend authenticity to their stories. Under the Lindley rule," even these advices are prohibited. The reporter must state the information on his own authority.

Mr. Lindley was born in Richmond, India. He attended Indiana University, where his father was a professor of philosophy, served in the Army in World War I, and graduated from the University of Idaho. He was awarded a Rhodes Scholarship and spent three years at Oxford University in England.

His career in journalism dated from his college days as a campus correspondent for West Coast and Idaho newspapers. He also filled in at one juncture for the editor of the Moscow Idaho, Star Journal. His first full-time newspaper job was on the Wichita Daily Beacon.

In 1924, Mr. Lindley joined the staff of The New York World as a reporter and political writer. He moved to The Herald Tribune in 1931 when the world ceased publication.

Mr. Lindley's prolific literary production included the first book about Roosevelt, "Franklin D. Roosevelt -- A Career in Progressive Democracy." He also wrote "The Roosevelt Revolution -- first Phase," "Half Way with Roosevelt" and "How War Came -- U.S. Foreign Policy from the Fall of France to Pearl Harbor." With the former Mary Grimes, whom he married in 1929 and who died in 1976, he wrote "The New Deal for Youth."

Mr. Lindley was a winner of many journalistic awards and was the holder of several honorary degrees. In 1974, he was elected a scholar by the Distinguished Alumni Service Award Club of Indiana University. This carried with it a grant for the preparation of Mr. Lindley's memoirs, which he then undertook to write.

Survivors include his wife, the former Jean Rasch Gehman, of the home in Washington; three sons, Jonathan, of Alexanderia, Christopher, of Rochester, N.Y., and Mark, of St. Louis; a brother, Stanley of Michigan, and seven grandchildren. CAPTION: Picture, ERNEST K. LINDLEY