Preheat the oven to 350 degrees. Spray 9x13" pan with nonstick spray.
Mix the cake mix, oats, butter and 1 egg. Reserve 2 cups for topping. Press remaining crumb mixture into the bottom of pan.
Blend frosting, cream cheese, sour cream, and remaining 2 eggs and pour over pressed crumbs.
Sprinkle the reserved crumb mix over the top and bake for 45-55 minutes. Cool to room temperature and then store in the refrigerator. Sprinkle with powdered sugar before serving, if desired.