Peter H. Dominick, 65, a former Republican member of the House of Representatives and the U.S. Senate from Colorado who was known for his generally conservative views on issues such as taxes and labor and the intelligence with which he could explain them, died at his home in Hobe Sound, Fla., Wednesday following a heart attack.

Mr. Dominick was defeated in 1974 in his bid for a third term in the Senate by Gary Hart, a young Democrat who had served as a top aide to senator George McGovern of South Dakota in the 1972 presidential campaign. Richard M. Nixon won that election by a landslide. Hart is now Colorado's senior senator.

A prosperous attorney from Denver who had served successfully in the Colorado legislature in the 1950s, Mr. Dominick was elected to the House of Representatives in 1960. Two years later, he defeated John A. Carroll, the incumbent Democrat, for a seat in the Senate. He served there until 1975.

After Mr. Dominick's defeat at the hands of Hart, president Gerald R. Ford appointed him ambassador to Switzerland. He was able to serve only briefly because of the onset of multiple sclerosis.

Mr. Dominick came to prominence in Colorado and national politics in tandem with John Love, another bright young Republican who was elected governor of the state three times beginning in 1962. Mr. Dominick and Love were regarded as representatives of a bright new generation of politicians in their state. Love was elected governor of Colorado three times beginning in 1962. He later came to Washington as an energy czar in the Nixon's administration. Among the views that Mr. Dominick and Love shared were the conviction that Democrats in Washington were interfering unduly in the affairs of the western states and that taxes were too high.

In the Senate, Mr. Dominick served on the Armed Services and Labor and Public Welfare committees. He also served on the Joint Committee on Atomic Energy. Earlier, he served on the Senate District Committee. On issues such as occupational health and safety he opposed efforts to strengthen the enforcement side of that program. On Watergate, he remained a Nixon loyalist long after many Republicans had begun to express doubts about the president's position.

Peter Hoyt Dominick was born in Stamford, Conn., July 7, 1915. He graduated from Yale University and earned a law degree there in 1940. During World War II, he was a pilot in the Army Air Corps and won the Distinguished Flying Cross and two Air Medals flying B24 Liberator bombers over "the Hump" from India and Burma into China.

After the war, he moved to Denver and became a member of the law firm of Holland & Hart. He became active in Republican politics in the first Eisenhower campaign in 1952. He was elected to the State House of Representatives in 1956 and served there until he went to Congress. Reporters covering the statehouse voted him the best first-year state representative. During his second term, he was voted the most effective House Republican.

Mr. Dominick, who maintained homes in Hobe Sound and Cherry Hills, Colo., is survived by his wife, the former Nancy Parks; three sons, Peter H. Jr., of Denver, Michael Parks, of Boulder, Colo., and Alexander Smith, of Washington; one daughter, Lynne Dominick Arena of Washington; one brother, Bayard, of Connecticut, and five grandchildren.