The Rebels trailed 26-10 at half, and 40-18 after three.
Sioux Central drops to 4-14 with the loss, their seventh in a row. Points have been hard to come by in that stretch with 45 as their high during the current drought.
The Rebels shot 8-of-42 from the floor Thursday, including 1-of-11 from three. They were 14-of-23 at the foul line.
"We really had a hard time getting into any offensive flow," said Sioux Central head coach Stephen Tjaden. "That's a great credit to South O'Brien's defense. Our effort on the defensive end was not where it needed to be if we want to compete with good teams. We need to make some improvements as we enter the final week of the regular season before district play."
Austin Glawe led the way in the loss with 21 points on 5-of-22 shooting. He added 17 rebounds and two blocks. Tim Saunders followed with five points and four rebounds, Christian Sylvester scored three and Karver Brown two.
Brett Puhrman led South O'Brien with 15 points. They have now won six straight to improve to 13-6.
Sioux Central hosts Clay Central-Everly Monday night and Newell-Fonda Tuesday.