Preheat the oven to 350℉. Spray a 9x13-inch pan with nonstick spray.
In a medium bowl, cream the butter; stir in the oats, sugar, corn syrup and vanilla. Spread the mixture into the prepared pan. Bake for 15 minutes. Cool.
In a microwave-safe bowl, melt the chocolate chips and peanut butter in short bursts in the microwave; stir to combine. Spread over the cooled bars. Chill for several hours before cutting into bars.