[2] Parsons returned to the field in 1947 as assistant to Myron Charles Taylor, the Personal Representative of the President of the United States to the Vatican, a post he held until 1948.

[2] Returning to the U.S. in 1950, Parsons was posted at the National War College, and then in 1951 became Deputy Director of the State Department's Office of European Regional Affairs.

Parsons continued to support the administration's Laotian policy in 1959-61, during which time he served as Assistant Secretary of State for East Asian and Pacific Affairs.

[3] On March 15, 1961, President John F. Kennedy named Parsons United States Ambassador to Sweden, heading up the embassy in the Diplomatstaden, Stockholm.

Closely identified with American policy towards Southeast Asia, Parsons became the focus of criticism in Sweden as Swedish opposition to the United States' role in the Vietnam War mounted throughout the 1960s.

Parsons served as deputy chairman of the U.S. delegation to the Strategic Arms Limitation Talks from 1970 until he retired from the Foreign Service in 1972.