Ohio State has won or shared the past six Big Ten titles, and the Buckeyes were picked to make it seven before the season began, but they entered the day closer to the bottom of the standings than the top.
The Lady Lions, meanwhile, entered the day in a first-place tie and left little doubt about why.
With a balanced scoring attack that included five players scoring in double figures, Penn State (18-5, 7-2) controlled most of the action in front of 6,618 fans at the Bryce Jordan Center in Happy Valley.
Penn State freshman Maggie Lucas made a three to break a 15-all tie with 12:18 to go in the first half and begin an 11-2 run that also included four points apiece by post players Nikki Greene and Mia Nickson.
The Lady Lions' lead eventually peaked at 13 points when point guard Alex Bentley nailed a pull-up jumper with 3:46 to play in the first half.
That's when the Buckeyes (13-8, 4-5) showed some life.
The Lions took a 39-33 lead into the locker room at halftime thanks to the steadying influence of Bentley, who hit four free throws in the last 1:06 of the half.
Her pair of trips to the charity stripe sandwiched one for Ohio State's Tayler Hill, who made a pair of freebies to account for the Buckeyes' last two points of the stanza.
The Lions pushed their lead back to 10 early in the second half before Hill ignited an 7-0 OSU run by drawing a foul on Bentley and completing an old-fashioned three-point play.
Prahalis followed with a short jumper and a pair of free throws to cut the deficit to 43-40, but that was a brief ray of sunlight for the visitors.
Bentley stopped the run with a floater then Lucas nailed a three-pointer after being left alone in the left corner.
After Ohio State's Ashley Adams made 1 of 2 free throws, Lucas drained a trey from the other side of the floor, making the PSU lead 10 again.
A few minutes later, another Lucas triple, her sixth of the game, allowed the Lions to go up 13 with 13 minutes left.
Ohio State had a handful of chances to get back in the game before it was over, but the Buckeyes could not come up with the shots or the stops they needed to break through.
Penn State feasted off turnovers, scoring 20 points on 14 OSU miscues, and added 15 second-chance points on 15 offensive rebounds.
Executing on those chances turned out to be key as the Buckeyes forced 13 turnovers and grabbed 10 offensive rebounds but scored only eight and seven respective points as a result.
Lavender led all scorers with 26 points while Hill added 18 and Prahalis had 11.
Bentley topped the victors by tallying 21 points and handing out seven assists.
Lucas notched 18 points, Julia Trogele had 14, Greene had 12 and Nickson 10.