[3][4] O'Neill began attendance at Georgetown University in the fall of 1964, and he received his Bachelor of Science in foreign trade in 1968.

[5] While in college, O'Neill took part in the Reserve Officers' Training Corps program and served as secretary of the Scabbard and Blade Society.

[5] After college, O'Neill began attendance at Georgetown University Law Center, from which he received his Juris Doctor in 1971.

[6] After his military service, O'Neill was a law clerk in 1972 for Judge Sylvia Bacon of the Superior Court of the District of Columbia.

[6] From 1972 to 1973, he was a law clerk for Judge Albert Wheeler Coffrin of the U.S. District Court for Vermont.