Patterson could face as many as 25 years in prison when he is sentenced in April, prosecutors said.
Two other men — Kevin James, 31, and Levar Haley Washington, 28 — pleaded guilty in the case last week. A fourth, Hammad Riaz Samana, has been declared mentally unfit to stand trial and is undergoing psychiatric care at a federal prison.
All except Samana, a citizen of Pakistan, are American-born Muslim converts. The men were indicted in 2005 for what authorities said was a plot to attack American military facilities, Israeli government offices and synagogues in the Los Angeles area.
Prosecutors said the plot was orchestrated by Washington, Patterson and Samana at the behest of James, an inmate at California State Prison in Sacramento and founder of the radical Muslim group Jamiyyat Ul-Islam Is-Saheeh.
Patterson has cooperated with authorities, according his attorney, Winston Kevin McKesson.
"He volunteered to work for the government after finding out James lied," McKesson said. "James misled them in what the Quran says."
The plotters were within weeks of being able to carry out an attack before they were discovered about two months before the Jewish holiday Yom Kippur, officials said. Police uncovered the plot in July 2005 while investigating a string of gas station robberies that authorities say were committed to finance the attacks.
