As a student, Allen majored in history at Stanford University and studied at California State University, Long Beach. He was a prominent member of the John Birch Society, of which he was a spokesman. He contributed to magazines such as Conservative Digest and American Opinion since 1964. He also was the speech writer for George Wallace during the Alabama Governor Presidential campaigns and was adviser to the conservative Texas millionaire Nelson Bunker Hunt.
In 1972, Allen wrote with Larry Abraham None Dare Call It Conspiracy (prefaced by Congressman John G. Schmitz), a best seller which achieved sales of over five million copies worldwide during the United States presidential election.
In this book, Congressmen John G. Schmitz says in the Introduction, "The story you are about to read is true." Allen goes on to assert that the present political and economic systems in most developed nations are the result of a sweeping conspiracy by the Establishment's power elite, which started in the early 1900s. According to this theory, this has been a four-step process:
- Establish an income tax system as a means of extorting money from the common man;
- Establish a central bank, deceptively named so that people will think it is part of the government;
- Have this bank be the holder of the national debt;
- Run the national debt, and the interest thereon, sky high through wars (or any sort of deficit spending), starting with World War I.
As an investigator of U.S. financial, industrial, and political elites, Allen wrote other books about the Council on Foreign Relations and the Trilateral Commission, asserting that the term "New World Order" was used by a secretive elite dedicated to the destruction of all national sovereignties. Allen's last book, Say "No!" to the new world order, was published posthumously in January 1987.
- Communist Revolution in the Streets, Western Islands, 1967
- Nixon's Palace Guard, Western Islands, Western Islands, 1971
- Richard Nixon: The Man Behind the Mask, Western Islands, 1971
- None Dare Call It Conspiracy, Concord Press, 1972 (ISBN 0899666612)
- Jimmy Carter, Jimmy Carter, '76 Press, 1976
- Kissinger: The Secret Side of the Secretary of State, 76 Press, 1976
- The Rockefeller File, '76 Press, 1976
- Tax Target, Washington, '76 Press, 1978
- Ted Kennedy: In Over His Head, '76 Press, 1981
- Say "No!" to the New World Order, Concord Press, 1987
- . The New York Times. December 2, 1986.
- Ronald Lora, William Henry Longton, The Conservative Press in Twentieth-Century America, Greenwood Press, 1999, p.507
- None Dare Call It Conspiracy, 1971
- anonymous; "Gary Allen, 50, Dies in West; Spread Conservatives' View", Associated Press, published in The New York Times on December 2, 1986.
- Willie Maartens, Mapping Reality A Critical Perspective on Science and Religion, iUniverse, 2006, p. 272
- Leibovich, Mark; "The Man The White House Wakes Up To", New York Times Magazine; 19 April 2010.
- Gary Allen, with Larry Abraham and Introduction by Congressman John G. Schmitz (First Printing February, 1972). None Dare Call It Conspiracy. GSG & Associates Publishers. Retrieved 2012-11-02.
- Michael Billig and Jovan Byford, "The emergence of antisemitic conspiracy theories in Yugoslavia during the war with NATO", Patterns of Prejudice, October 2001
- Council on Foreign Relations (November 25, 1959), Study NO. 7, CFR, Office of the Federal Register – National Archives and Records Administration, retrieved 2012-11-02
- Jesse Helms (September–October 1996), Fixing The UN, Foreign Affairs, retrieved 2012-11-02
- Berlet, Chip (Fall 1998, revised 4/15/99). Dances with Devils: How Apocalyptic and Millennialist Themes Influence Right Wing Scapegoating and Conspiracism. Retrieved 2009-07-23.
- Daily Bell: Gary Allen Biography
- Internet Archive Community Books: None Dare Call It Conspiracy (1972)
- Open Library: Gary Allen