The Buckeyes (28-4) took an early 5-3 lead at the 16:45 mark of the first half and were never headed, building their lead to as much as 12 points in the opening 20 minutes and 16 points with 8:47 remaining in the game.
But the Fighting Illini (16-14) doggedly kept nipping at OSU's heels thanks to a series of mini-runs. Illinois got the deficit down to six points at 59-53 with 1:00 remaining but that was as close as they could get.
"It was a game of runs," Ohio State head coach Jim Foster said. "When they were coming at us at the end, we switched out of our zone defense into a man and the girls did what we expected them to do. When we went to man, we had great position and great communication."
Illinois head coach Jolette Law credited the Buckeyes for playing a stingy defense throughout the contest, and that led her team to miss 11 of their first 14 shots from the floor and finish 24 for 60 (40.0 percent) for the game.
Still, Law thought her team was its own worst enemy as it committed 10 first-half turnovers and put itself in a 33-24 hole at the break.
"We didn't play with very much confidence in the first half," the Illinois coach said. "We were a little unsure, a little tentative. Give a lot of credit to Ohio State. They got those loose balls we should have gotten."
The Buckeyes grabbed nine steals, including three each by senior Shavelle Little and sophomore point guard Samantha Prahalis, giving Ohio State a total of 33 steals in three games this season against the Illini. Little had 11 of those, including a career-high eight when the teams met in Champaign in late December.
"I have been stressing (turnovers) to my team for the last month," Law said. "Little is great. When she played us at our place, she was a one-woman press. You know she's going to get her steals and those are turnovers she forces. But we had a lot of unforced turnovers and when I look at the stats, I see our turnovers and the fact they had 18 points off our turnovers. That's a big difference."
It was a ragged first half with neither team seemingly getting its early bearings. While Illinois was making only 3 of its first 14 attempts from the floor, Ohio State wasn't much better. The Buckeyes were 4 of 12 with the main culprit being junior center Jantel Lavender. The three-time conference player of the year missed her first four attempts and six of her first seven.
But when Lavender hit her first shot at the 13:06 mark of the opening half, it gave her team a 12-7 advantage and kicked off a 12-4 run for the Buckeyes over the next 3½ minutes. Prahalis capped the run to push the OSU lead to double digits for the first time at 22-12 with 9:31 to go until the break.
Illinois made a mini-run of its own, outscoring the Buckeyes by a 7-2 margin over the next three minutes to pull with five at 24-19. But Ohio State responded by scoring nine of the half's final 13 points for a 33-24 advantage at the break.
The Illini made another run at the beginning of the second half, getting a basket from three-time All-Big Ten center Jenna Smith and a three-pointer from sophomore guard Lydia McCully inside the opening minute. That cut the Buckeyes' lead to four at 33-29 at the 19:03 mark.
OSU then went on another run of its own, scoring 22 of the game's next 32 points to seemingly put the game away at 55-39 with 8:47 left. But Illinois refused to give up. It went on a 12-2 run to get the game back to a manageable six points at 57-51 when freshman forward Karisma Penn hit a jumper at the 5:03 mark.
It remained a six-point game into the final minute when Ohio State turned up the defense. With precious seconds ticking down, the Illini couldn't find decent looks and were forced to put up low-percentage shots.
Then with the clock under 30 seconds and the Buckeyes holding a 61-53 lead, Little picked McCully's pocket at the top of the key for her third steal of the game. The Illinois turnover resulted in a layup for OSU freshman Tayler Hill with 26.4 seconds remaining and the Illini were never able to threaten again.
Lavender made up for her cold first half by making 5 of 6 shots in the second half to finish with a game-high 19 points. Junior Brittany Johnson added 13 points, a total matched by Prahalis who also passed out a game-high eight assists. Junior forward Sarah Schulze added eight points and a team-high eight rebounds.
Smith led Illinois with 13 points and a game-high 13 rebounds. Senior forward Lacey Simpson also had 13 points while McCully added 11.
Ohio State advanced to the Big Ten tournament semifinals to meet the winner of the Wisconsin-Purdue game. Tip-off for the semifinal is approximately 7:30 p.m. Saturday.