In front of 828 at Assembly Hall in Champaign, Ill., Ohio State led 38-29 at the half and extended that advantage to 12 in the opening five minutes of the second stanza.
Illinois used a 14-1 run to take a 50-49 lead at the 9:30 mark, but Ohio State responded like a team hungry for its first Big Ten road win.
Seconds after Lydia McCully put the Fighting Illini ahead with an old-fashioned three-point play, Brittany Johnson found herself all along in a corner and drilled a three-pointer to put Ohio State back on top.
Freshman center Ashley Adams, playing by far the best game of her young career, extended No. 25 Ohio State's lead to four with a basket in the paint and later added a free throw to make it 55-50.
She then intercepted an Illinois pass to start a break that led to teammate Tayler Hill's drive that earned a pair of free throws, and Ohio State quickly re-established a seven-point advantage with 6:32 left.
The closest the hosts would get the rest of the way was four points after a pair of Adrienne Goldbold free throws made it 63-59 with 1:39 to go, but Johnson had one dagger left.
The senior from Olney, Ill., got open in the corner again and buried her seventh three-pointer of the game to stretch the Buckeyes' advantage back to seven points with 1:22 on the clock.
Ohio State (12-6, 3-3) closed out the game with four free throws by Hill and another from Lavender.
Johnson made 7 of 12 treys and finished with a team-high 22 points in her final collegiate game in her home state. She also had four rebounds and a pair of steals.
Lavender, the senior three-time All-Big Ten center, posted 19 points and 12 rebounds while her 6-5 freshman protege, Adams, had a career-high 13 points and nine boards.
Adams blocked five shots, three steals and four assists in 25 minutes.
She was part of a group of three who replaced injured senior Sarah Schulze.
Freshman Martina Ellerbe started the game in Schulze power forward spot and made a pair of steals while guarding Illinois star Karisma Penn, but head coach Jim Foster eventually decided to go with the twin tower lineup of Adams at center with the 6-4 Lavener sliding over to power forward.
Alison Jackson also saw some time in Schulze's old spot, notching one point and a pair of rebounds in 13 minutes.
Hill, who played much of the second half at point guard while All-Big Ten junior Prahalis sat the bench, finished with 10 points despite going 0 for 10 from the field. Hill made 10 of 12 free throws and grabbed 10 rebounds. She had no assists and one turnover in 34 minutes.
Penn led Illinois (7-12, 2-4) with 26 points and 18 rebounds. She also had four steals. None of her teammates cracked double figures in scoring.