Lyonell Gaines scored four points in overtime for Morehead State, including a putback with 32 seconds left to tie it before Petros hit the game-winner.
Petros had 25 points and 10 rebounds, and Kahlil Felder 13 points and seven assists to lead Oakland (4-5).
Angelo Warner scored four points during an 11-2 run to give Morehead State a 61-59 lead with 2:06 remaining in regulation. Dante Williams split a pair of free throws and Felder and Petros scored to give Oakland back the lead, 64-61 with 38 seconds left. Corban Collins drained a trey to tie it with 29 seconds to go, and Petros missed a layup to send it to overtime.
Gaines had 18 points and 10 boards to lead Morehead State (4-7).