O’Neale was 5 of 7 from the field, while Griffin was 3 of 5 and had four rebounds.
Chase Hallam scored 11 points, and Brett Olson and Nate Engesser scored 10 points apiece. Chris Udofia had seven points, four rebounds and seven assists.
Southern Utah had a one point lead early in the first half, but Denver (4-6) led 40-20 at halftime and never looked back. The Pioneers shot 55 percent from the field for the game, while the Thunderbirds shot 40.8 percent.
Jackson Stevenett led the Thunderbirds (3-7) with 12 points. Jayson Cheesman added 10 points and six rebounds. Wade Collie had nine points, all from 3-point range.
This was the third-straight home win for the Pioneers.