Edward Zorinsky, the maverick senior senator from Nebraska who unabashedly switched from Republican to Democrat to run for the Senate in 1976 and then threatened to switch back four years later when the Democrats lost power, died late Friday in Omaha of a heart attack at the age of 58.

Zorinsky, who reportedly collapsed after singing at a dinner at the Omaha Press Club at 10:45, was taken by ambulance to Methodist Hospital and died a short time later, according to state Sen. Bernice Labedz, a longtime friend.

He had been receiving treatment for a heart ailment for several years, and was hospitalized in 1985 after suffering chest pains.

Zorinsky, born Nov. 11, 1928, was the son of a Russian Jewish immigrant. He did postgraduate work at Harvard University before returning to Omaha to run a family wholesale tobacco and candy business. He got his first taste of politics as a member of the public utilities board, and went on to become mayor of his home town at age 45.

A lifelong Republican, he broke ranks when the local hierarchy nominated another candidate for the U.S. Senate in 1976, and ran as a Democrat, winning handily. In 1980, when the Republicans rode Ronald Reagan's victory back into control of the Senate, Zorinsky briefly flirted with the possibility of switching back, but he and Nebraska Republican Party leaders could not come to terms.

Independent, cranky, conservative to the point of parsimony and as adept at seeking compromise in the partisan desert as a water dowser, Zorinsky repaid his constituents' faith by making farm belt issues his top priority.

The ranking Democrat on the Agriculture Committee, Zorinsky pushed for programs aimed at expanding credit for hard-pressed farmers and speeding up the electrification of rural areas. He expended considerable energy attacking the Carter administration's embargo on grain sales to the Soviet Union, and had become increasingly active in the area of agricultural trade policies.

"Rural America never had a better friend," Senate Minority Leader Robert J. Dole (R-Kan.) said early today. "Ed was a courageous, dedicated public servant who never stopped working for his constituents . . . . I join Nebraska in mourning the passing of this good man."

Zorinsky was also a member of the Foreign Relations Committee, where his maverick tendencies made him a swing vote; Congressional Quarterly once described him as having supported Reagan more often than any Democratic senator outside the South. But he also frequently joined with more liberal Democrats in opposing the administration's policies in Central America.

Zorinsky also had a flair for personal, but highly publicized, tightfistedness. He made an annual ceremony of returning to the U.S. Treasury money he could have spent on staff salaries -- nearly $1.7 million in his first term alone. In a famous burst of Midwest economizing, he once had an aide steaming uncanceled postage stamps off incoming mail until he was informed their reuse was illegal.

He also turned his frugality like a weapon on the government bureaucracy, holding up multibillion-dollar legislation for in-depth cost-efficiency studies and ordering an audit of the Federal Farm Insurance Corp. that eventually trimmed that agency's budget by removing some of the more free-handed officials.

He also was known for a literal open-door policy: He took the door of his Capitol Hill office off its hinges, saying, "I never close the door on anything."

His wife, the former Cece Rottman, was with him when he died, a hospital spokeswoman said. He also leaves three children.

JOHN WILLIAM STONE, 68, a retired official with the old Naval Materiel Command who later became vice president of Delex Systems Inc., a consulting firm in Vienna, died March 5 at Carroll Manor Nursing Home in Hyattsville. He had Parkinson's disease.

Mr. Stone was born in Thornton, Wash. He graduated from the University of Idaho and moved to the Washington area during the early 1940s. During World War II, he served in the Navy.

After the war, he worked for the Navy Department as an engineering draftsman, mechanical engineer and electrical engineer. In the early 1960s, he worked for the National Aeronautics and Space Administration as chief of post-Saturn vehicle studies.

In 1964 he returned to the Navy Department to work for the Naval Materiel Command as a technical adviser and as head of the systems effectiveness branch. He retired in 1974 and received the Navy's Special Achievement Award and the Superior Civilian Service Medal.

From 1975 to 1979, Mr. Stone was vice president of Delex Systems.

Survivors include his wife, Anne Marie Stone of Silver Spring; one daughter, Jean Marie Reilly of New York City; two sons, John E., of Arlington and Michael, of Washington; one sister, Melissa Covington of Fullerton, Calif., and one brother, Robert E., of Santa Cruz, Calif.

BETTE RILEY TRAMONTIN, 62, a retired secretary at the Environmental Protection Agency and a longtime resident of the Washington area, died of peritonitis March 4 at the Shands University Teaching Hospital in Gainesville, Fla. She had undergone intestinal surgery.

Mrs. Tramontin, a resident of Palm Coast, Fla., was born in the Bronx, N.Y. She grew up in Washington and graduated from Western High School. She attended Wilson Teachers College and George Washington University.

In the early 1960s she worked for an insurance company in Washington. She later joined the federal government. In 1974, when she retired for reasons of health, she was a secretary at the EPA.

Mrs. Tramontin was a member of St. Jude's Catholic Church in Rockville and she lived in Rockville until moving to Florida in 1980.

Her first husband, Jeremiah T. Riley, died in 1980.

Survivors include her husband, William F. Tramontin of Palm Coast; three children by her first marriage, John T. Riley of Washington and Timothy S. and Constance Riley, both of Gaithersburg, and three brothers, three sisters, and a grandchild.

LINDA B. GOLDMAN, 46, director of legal assistance for the International Monetary Fund, died of cancer March 6 at Georgetown University Hospital.

Mrs. Goldman, a resident of Bethesda, was born in Kansas City, Mo. She graduated from Southern Methodist University, where she also earned a master's degree in international studies. She earned a second master's degree at the Johns Hopkins School for Advanced International Studies after moving to the Washington area in the mid-1970s, and she also graduated from American University Law School.

She practiced law with the firm of Akin, Gump, Strauss, Hauer and Feld in Washington until 1981, when she became director of legal assistance for the World Bank and the IMF. In 1984 she began working exclusively for the IMF.

Mrs. Goldman's marriage to Fernando Cabezas ended in divorce.

Survivors include her husband, Robert Kogod Goldman, and a son by her first marriage, Francis H. Cabezas, both of Bethesda; her mother, Mrs. Frank R. Brown Jr. of Independence, Mo., and a brother, Dr. Frank R. Brown III of Charleston, S.C.

PATRICIA HODGINS ONDRICK, 80, retired investments accounts manager in Chicago and Los Angeles who moved to this area in 1978, died of cancer March 6 at a hospital in White Plains, N.Y., where she was staying with her daughter.

Mrs. Ondrick, who lived in Silver Spring, was born in Sioux City, Iowa. She graduated from Northwestern University. She retired in the early 1940s from a career in the investment business. She lived in San Antonio before moving to the Washington area nine years ago.

Her husband, retired Army Brigadier Gen. John G. Ondrick, died in 1974. Survivors include two daughters, Mrs. Wilbur S. Jones of Wheeling, W.Va., and Mrs. Joseph A. Maria of White Plains, and four grandchildren.