Stuart Schulberg, 56, executive producer of news documentaries for the National Broadcasting Co. and former producer of its early morning "Today" show, died Thursday at Beth Israel Hospital in New York City. The cause of death was not disclosed.

He produced the "Today" show from 1968 to 1976, longer than any other person in the award-winning program's history. During that time, the show was the undisputed ruler of early morning network hours.

In that period Mr. Schulberg won two Emmys for the "Today" show and another two Emmys for "David Brinkley's Journal."

He left "Today" to become executive producer of documentaries. His recent assignments included the NBC News Special Report, "College Sports Inc. - Big Money on Campus," aired on April 29, and "The American Family - An Endangered Species?" a three-hour program presented last Jan. 2.

Mr. Schulberg was born in Los Angeles, the son of the late B.P. Schulberg, at one time a major Hollywood producer. He was the younger brother of Budd Schulberg, the well known author, screenwriter and producer.

He attended the University of Chicago and schools in Geneva, Switzerland, and London.

Before World War II, Stuart Schulberg was a sportswriter and reporter for the old Washington Daily News. He served with the Marine Corps and the Office of Strategic Services during the war and then organized and headed a documentary film unit of the U.S. military government in West Germany.

In 1949, he joined the film section of the Economic Cooperation Administration in Paris as deputy chief and later became chief of the section, supervision some 200 documentaries and information films.

Before starting work with NBC in 1961, Mr. Schulberg had joined his brother, Budd, in adapting the latter's novel, "What Makes Sammy Run?" for NBC's "Sunday Showcase." The brothers also were coauthors of the libretto of a Broadway musical version of the show.

In addition, Mr. Schulberg produced or coproduced such feature films as "No Way Back," "Wind Across the Everglades" and "Special Delivery."

In addition to his brother, survivors include his wife, the former Jane Murphy, and four children, Sandra, Jonathan, Peter and Kevin, from a previous marriage that ended in divorce. CAPTION: Picture, STUART SCHULBERG