Preheat oven to 350 degree F.
Spray a 9-inch by 11-inch baking pan with oil; set aside. In a large mixing bowl, cream butter and sugar until light and fluffy. Add vanilla and corn syrup; mix well. Stir in oats. Pat mixture into prepared pan and bake for 15 minutes. (It won't look done, but take it out anyway.)
In a microwave-safe bowl, heat chocolate and peanut butter on medium for 1 minute. Stir to fully melt. Spread mixture over crust. Chill. To serve, cut into 32 pieces.