Bell, making his first career start, completed 22-of-30 passes for 232 yards while rushing 12 times for 59 yards as the Sooners (4-0) picked off Fighting Irish quarterback Tommy Rees three times.
Oklahoma intercepted back-to-back Irish passes less than 3 minutes into the game -- one that resulted in Nelson's 24-yard touchdown and a second that set up an 11-yard TD run from Damien Williams.
The Sooners racked up a ninth straight regular-season victory since their Nov. 5 loss to Notre Dame last season.
Rees completed just 9-of-24 passes for 104 yards and two touchdowns to go along with the trio of pick-offs.
George Atkinson III ran for a career-high 148 yards with a score on 14 carries for the Fighting Irish (3-2), fell to Oklahoma for the first time since 1956.
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