Buckeye freshman Tayler Hill stopped that spurt with a three-pointer from the left wing, but Northwestern's Kendall Hackney hit a turnaround jumper in the lane and teammate Beth Marshall added a three from the left wing to draw the visitors within seven.
Ohio State (27-4, 15-3) still managed to take a 30-25 lead into the locker room at halftime, but only after Hackney missed a shot from point-blank range with 28 seconds left that could have made it a one-possession game again.
The Wildcats hung around despite shooting 34.5 percent (10 for 29), including 22.2 percent (2 for 9) from three-point range.
Ohio State made 12 of 30 shots (40 percent) and canned 4 of 12 treys (25 percent).
The Buckeyes blew the game back open at the start of the second half by scoring 17 of the first 20 points.
With four assists and five points, Ohio State point guard Samantha Prahalis had a hand in every basket but one during the run.
That established a 47-28 lead with 14:45 left, and the Wildcats (16-12, 7-10) never threatened again.
The Buckeye lead peaked at 31 with 1:13 left to play.
When it was over, the Buckeyes cut down the nets and accepted the Big Ten championship trophy they actually earned a full two weeks earlier with a 75-45 defeat of Purdue on Feb. 11.
All in all, it made for an eventful night, and some on the Ohio State side admitted some of the emotion of Senior Night might have contributed to the lackluster first half.
"It was really emotional coming in knowing it's your last game to play in the Schott," said senior Maria Moeller, who scored nine points. "There were a whole bunch of emotions flowing in the first half, and maybe that affected us, but we regrouped at halftime and came out with a strong second half."
Added Lavender, who had game highs of 26 points and 12 rebounds, "I think we really looked at ourselves at halftime and said it's Senior Night, but we have to get past all this emotion and just come out and play extremely hard. Don't let teams feel like they have a chance early, don't let people hit shots or let the defense get broken down.
"I think we just came together and decided we wanted to play extremely hard on defense. We wanted the seniors to go out with a bang, so we just had to turn it up a couple notches."
To make matters better for the 5,429 in attendance, all four of the seniors got into the act at one point or another.
Walker swatted a pair of shots in the first half, and in the second she contributed a reverse layup, showing off what has become a surprising signature move for a center who stands 6-5. Later, she rejected another shot to force a shotclock violation with 35 seconds remaining.
Moeller delighted the crowd with a pair of three-pointers 70 seconds apart just after the midway point of the second half.
Two-time Big Ten Defensive Player of the Year Shavelle Little notched one of her signature stats - a steal - by going to the floor to dig a ball loose at the 4:46 mark, leaving the only suspense whether or not fellow guard Cherise Daniel would find a way to write her name in the scorebook in her last game in her hometown.
The Columbus Eastmoor Academy product's first attempt to score was a somewhat skittish looking layup that hit glass but no rim around the 4-minute mark.
She had another chance in the lane three minutes later but instead dumped the ball to Little, who laid it in for her only basket of the night.
As time wound down, it became clear the fans and Daniel's teammates hoped to see her score, but such a fairytale ending was not in the cards. Daniel's last shot attempt fell short as the final buzzer sounded.
The Buckeyes turned up the defense in the second half, forcing 10 turnovers and 30 percent shooting (9 for 30) from the floor.
Their defense made pushed the ball up the floor quickly an easier proposition, leading to a 14-0 Ohio State advantage in transition points.
Much of that was thanks to Prahalis, who had 14 points and tied a career high with 14 assists.
"I think the second half, that's who we are," Ohio State head coach Jim Foster said. "Sometimes we forget."
Ohio State scored more points in the second half (48) than it allowed for the entire 40 minutes, and the Buckeyes beat Northwestern for the 19th straight time, a streak that spans all of the previous decade.
"Were real happy to play that way in the second half," Foster continued. "I think we've been spending the last two weeks figuring out how we should act. I've been doing this for 32 years and I've never clinched a championships with four games to go. How were we supposed to act? I think we finally figured it out in the second half. It's more fun. We all have more fun when we play like that. I know I do."
Big Ten play continues this weekend, but the Buckeyes have their second bye of the conference season.
They will return to action March 5 as the No. 1 seed at the Big Ten Tournament at Conseco Fieldhouse in Indianapolis.