Newell W. Ellison, 86, a retired senior partner in the Washington law firm of Covington & Burling, who was active in civic and professional organizations, died Saturday at the Chevy Chase Home in Washington after a stroke.

Mr. Ellison joined Covington & Burlington in 1921, became a partner in 1926, and was managing partner and head of the firm from about 1950 to 1965. He retired from active legal practice two years later.

In addition to maintaining a practive in civil, tax, and corporate law with one of Washington's largest and most prestigious firms, Mr. Ellison devoted much time to service on various judicial commissions.

In the early 1950s, he was chairman of the Council on Law Enforcement of the District of Columbia's Committee on Juvenile Crime. In the mid-1950s, he was chairman of the D.C. Board of Elections.

From 1968 to 1971, he chaired the Committee on the Administration of Justice, which was appointed by the Judicial Council of the District of Columbia. The committee recommended a major reorganization of the District of Columbia's courts and several innovations to improve the administration of justice. The bulk of the committee's recommendations were adapted.

One of the improvements the committee supported was the establishment of the D.C. Commission on Judicial Disabilities and Tenure. The Commission investigates complaints against judges and is invested with the power to remove or suspend a judge of the D.C. courts. Mr. Ellison served as the Commission's chairman from 1971 to 1975.

In 1969, Mr. Ellison was named "Lawyer of the Year" by the Bar Association of the District of Columbia. He was presented with a Certificate of Distinquished Service citing his outstanding work with the Association's administration of justice committee, particularly in the area of court reorganization. The citation went on to say that his contributions to the legal system "have won the admiration and respect of the Bench and of the Bar and have led this Association to award him its highest commendation."

Mr. Ellison served on the board of trustees of George Washington University from 1943 to 1969, and was the board's chairman from May 1959 to June 1965. A 1917 graduate of George Washington University and a 1921 graduate of its law school, he received the George Washington Law Association's distinquished alumnus aware in 1967.

He had been chairman of the American Bar Association's committee on facilities of the law library of Congress for three years, he was a fellow of the American Bar Foundation, the Washington Institute of Foreign Affairs, and was a past president of the Washington Foreign Law Society.

He was a member of the Metropolitan, Chevy Chase, 1925 F. Street, and Burning Tree clubs.

Mr. Ellison was a member of the Board of Trustees of the New York Avenue Presbyterian Church from the mid-1940s to the early 1950s.

He was a native of Parrottsville, Tenn., and a resident of Washington.

His wife, the former Anna Marie Kraus, died in 1961. His survivors include a daughter, Jon Brandt of Chevy Chase, and two grandchildren.