He received his Bachelor of Architecture degree from Catholic University of America in Washington, DC in 1953, and was a practicing architect working in the Washington, DC and Riverside, California areas of the United States.
An architect by trade, he began painting in the 1960s, and eventually became Riverside's premier watercolorist. O'Neill became the first resident of Southern California's Inland Empire to be accepted into the American Watercolor Society. After retiring from architecture, O'Neill took up watercolor painting more seriously.
O'Neill died of pancreatic cancer in 2007 at the age of 83. 2007 Elizabeth Callan Award from the American Watercolor Society
2005 Elizabeth Callan Award from the American Watercolor Society
1999 Work accepted into the 132nd Annual Exhibition of the American Watercolor Society. 1997 Second Place Award, Multi Media Exhibit XXVIII
1995 Best of Show Award, Riverside Art Museum Membership Exhibit
1994 Award of Excellence, Multi Media Mini XXV
1992 Accepted into 125th Annual Exhibit of the American Watercolor Society and granted Signature Membership
1990 Harrison-Cady Award American Watercolor Society 123rd Annual Exhibition
1989 Artist-in-residence, Na Bolom, San Cristobal Las Casas, Mexico
1988 Purchase Award for Permanent Collection, Palos Verde Community Art Exhibit
1987 Accepted into 120th Annual Exhibit of American Watercolor Society. and received the Edgar Whitney Award
1985 Acquisition Award for Permanent Collection, Mt San Jacinto College
1983 First Award, 8th Annual Heritage Awards exhibit, Inland
1982 First Award, Inland Exhibition XVIII, San Bernardino Co.
1982 Acquisition Award for Permanent Collection, Chaffey Community Art Association.
He was taken on as a pupil of Milford Zornes, and eventually became a signature member of Watercolor West, the National Watercolor Society, and the American Watercolor Society, and was the first Inland Empire resident to ever be accepted into the American Watercolor Society.