The Polar Bears improve to 4-1 overall and are 3-1 in OAC play, while the Crusaders fall to 2-3, 2-2.
Donley scored on touchdown runs of 23, 12 and 44 yards and senior Kyle Simmons completed 13 of 18 passes for 156 yards and ran 10 times for 54 yards for ONU.
Ryan Gunnarson had a big day for Capital, catching nine passes for 189 yards and a TD.
After a slow start, the Polar Bears got a spark when junior Jordan Chopp blocked a CU punt and gave ONU the ball near midfield early in the second quarter.
It took Northern seven plays to march 49 yards for a score, going up 7-3 when junior Seadrick Marshall scored from eight yards out with 10:06 left until halftime.
"No question that the blocked punt by Chopp was a big play in the game," ONU head coach Dean Paul said. "It gave us some momentum. Our defense played well all day and our offense picked it up in the last three quarters."
Senior Blair Ellenberger kicked a 23-yard field goal on ONU's next possession to make it a 10-3 game with 3:43 left in the second period.
Northern put the game away by scoring on five of its first six possessions in the second half.
ONU took the second half kickoff and marched 80 yards in 10 plays and went up 17-3 on a 23-yard run by Donley with 4:50 gone in the period.
Ellenberger then kicked a 37-yard field goal with 5"40 left in the third and it was 20-3 ONU.
The Polar Bears then marched 50 yards in eight plays and increased their lead to 27-3 on a 12-yard run by Donley with 29 seconds left in the third.
After an exchange of punts, senior Jesse Richards intercepted a pass and returned it 11 yards to the CU 19-yard line, setting up a 7-yard TD run on a reverse by senior Brook Crawford.
Freshman Luke Rice made the extra point and Northern led 34-3 with 10:46 remaining in the game.
Kory Hartinger hit Gunnarson on a 35-yard TD pass to pull CU within 34-10 with 9:53 to play.
But the Polar Bears responded by marching 63 yards in just three plays and scored on a nifty 44-yard run by Donley to make it 41-10 with 8:13 to play.
Another blocked punt this one by senior Zack Click, gave ONU the ball at the CU 2-yard line, setting up a 221-yard field goal by Rice with 1:09 left in the game to complete the scoring.
The Polar Bears out-gained CU 482-312, including a 326-76 advantage on the ground.
Capital dominated the first period, controlling the ball for 11:47 and forcing two Northern fumbles. But the Polar Bears survived, trailing only 3-0, and swung the momentum on Chopp's blocked punt early the second period.
Northern controlled the ball 29:30 of the game's final 45 minutes.
Senior linebacker Josh Bowman had eight tackles and Richards had seven tackles and an interception to lead the ONu defense.
The Polar Bears will return to action next Saturday against Baldwin-Wallace, who is 5-0 and tied for first place in the OAC.
The contest will kickoff at 1:30 pm at Dial-Roberson Stadium and will be televised on tape-delay throughout Ohio on SportsTime Ohio.