Breunig signed with Arizona State University out of Phoenix Alhambra High School and became a starter by his second year (NCAA football freshmen were then ineligible), leading the team in tackles with 91 (incl. 19 against the Air Force Academy). He would remain the team leader in tackles with 117 as a junior and 145 as a senior. He was a First-Team All American (Kodak, "Time Magazine", "Sporting News", Pop Warner), a Second-Team All American (AP and UPI), a two-time WAC Defensive Player of the Year and a three-time All-WAC selection. He played in the East-West Shrine Game, the Hula Bowl and the Coaches All-America Game.