The fourth-seeded Buckeyes, who enjoyed a significant height advantage over No. 13 seed UCF, started a bit shakily in their first game in 13 days but led by double-figures for much of the final 30 minutes in front of 5,658 fans at St. John Arena.
6-5 center Ashley Adam and 6-4 power forward Jantel Lavender both missed a couple of early looks from point-blank range, but the perimeter players picked up the slack in a 12-2 run that turned a 10-9 deficit into a 21-12 lead.
Guard Tayler Hill started the spurt with a fast-break layup that put the Buckeyes ahead 11-10 with 14:45 to go, and Brittany Johnson capped it with a three-pointer that made it 21-12, prompting UCF coach Joi Williams to call timeout with 12:13 on the clock.
After the Knights (22-11) drew within four just after the nine minute mark, Ohio State responded with a 7-0 run to establish a new largest lead.
After an Ohio State layup by Amber Stokes, Prahalis scored the final five points of the spurt, including a pair of fast-break layups, the latter of which made it 32-21 with 5:35 to go.
The Buckeyes (23-9) led 43-33 at the half and kept the Knights at arm's length throughout the final 20 minutes, leading by as many as 18 but never less than five.
The Knights made one last gasp in the final three minutes, drawing within 73-65 after a D'Nay Daniels three-pointer and a layup off a stolen inbounds pass 12 seconds apart, but the Buckeyes fended them off when Prahalis converted an old-fashioned three-point play after dribbling off most of the 35-second clock before driving to the rim for a layup.
That put the Buckeyes back up 11 with 1:21 to go.
"I can't say enough about how proud I am of our basketball team," Williams said. "We hung in there and fought. There were times that we could have easily given up. Ohio State did a great job."
She lamented her team's 18 turnovers leading to 28 Ohio State points.
"When you play a team of this caliber, you have very small room for error," she said.
Facing a team with no starters listed taller than 5-10, Lavender ended the day with 30 points and 10 rebounds. She tied former Oklahoma All-American Courtney Paris' NCAA record with her 134th double-figure scoring game, a mark she will get the chance to break Monday night when the Buckeyes face No. 5 seed Georgia Tech in a game scheduled to tip off around 7 p.m. The Yellow Jackets advanced with a 69-58 win over Bowling Green in the first game of the day at SJA.
"It's an NCAA mark, so I'll be in the rankings by myself," Lavender said when asked if the milestone was significant to her. "It takes a lot for someone to score over 10 points in that many games. It hasn't been a focus, but I always want to play well for my team. I'm going to be happy about that one."
Prahalis also posted a double-double as she scored 19 points and handed out 10 assists. She was in the middle of the action all day at both ends of the floor, a change from earlier in her career when she was known mostly for her flashy passing and scoring.
"I like them both," she said. "They both are kind of game changing and get the crowd involved."
Johnson added 14 points on 4 for 6 shooting that included three treys and became the 29th Buckeye to eclipse 1,000 points in a career.
Fellow guard Stokes contributed two points and pesky defense in 11 minutes off the bench.
"I thought we played sound defense," Ohio State head coach Jim Foster said after the Buckeyes held the Knights to 39.7 percent shooting (25 for 63). He was not disturbed by his undersized opponents' 15 offensive rebounds that led to 16 points.
"Look at the quality of the shots," he said. "We probably forced them into that area, so there's more than one way to look at it. You just don't look at the game numbers alone. Where are the shots? Where were the rebounds? Were they long rebounds? Et cetera. There's a lot of things. Part of their going to the offensive glass gave us 12 to 14 points in transition because they didn't have anybody back."
Daniels finished with 16 points for UCF, tying fellow forward Ashia Kelly for team-high honors.