He will lead his first performance of the 2006-07 season on September 23, in a program of film music.
O'Neil joined the Utah Symphony as assistant conductor in 2000 and was named associate conductor in 2002. He has guest conducted the Houston Symphony, Phoenix Symphony, Annapolis Symphony, Florida Philharmonic, Tulsa Philharmonic, and Salt Lake Symphony.
He has a master's degree in conducting from Rice University and a bachelor's degree in piano performance from the Oberlin Conservatory of Music.
O'Neil was chosen following an audition with the CSO last week; he succeeds Adam Flatt, who is concluding a five-year tenure with the orchestra in July.
Established in 1989 as the successor of the Denver Symphony, the CSO is the state's only full-time professional orchestra. Jeffrey Kahane is music director.