Bader broke the NCAA Division I career 3-point record last Sunday and went 6 for 13 in this game.
In a high scoring first half in which both teams shot over 56 percent, Youngstown State (15-16, 6-10) led The Golden Grizzlies 45-43 at the break.
The pace slowed with the start of the second period but Bader's jumper at 12:51 put Oakland (12-19, 7-9) up 54-53. Bader continued his 3-point assault as Oakland bumped the lead to 10 points with 3 minutes to play and rode it into the buzzer.
Oakland's Kendrick Perry scored 20 points before the break, but was held to 10 in the second half.
The two teams will pair off again on Tuesday (at Oakland) in the first round of the Horizon Conference tournament.