He attended Plainfield High School and St. Lawrence University.
During World War II, he served in the United States Army Air Corps in the Pacific Theater and Japan.
In 1971 he was elected to the New Jersey Senate to represent the 22nd Legislative District and served as chairman of the Transportation Committee.
[2] After his retirement from the Legislature, he founded the public affairs consulting firm, Peter J. McDonough and Associates.
His son, Peter J. McDonough Jr., was the director of communications for Governor Christine Todd Whitman.