Preheat oven to 350 degrees
Line 9" square pan with parchment & set aside
Combine cake mix, oil & eggs in mixer bowl & stir at a low speed until fully combined & smooth
Transfer batter into prepared pan & press into an even flat layer
Top with peppermint patties & press in slightly
Bake 25-30 minutes or until toothpick test comes out clean
Cool completely on wire rack before cutting & serving