Grease a 9"x9" pan with cooking spray and set aside.

Over medium heat, melt the two sticks of butter in large saucepan. Once melted, stir in the brown sugar and vanilla. Mix in the oats. Cook over low heat for about 5 minutes, until ingredients are well blended. Press half of mixture into the bottom of the prepared pan. Reserve the other half for topping.

Meanwhile, melt 1 cup of the chocolate chips (reserve the other cup for topping) and peanut butter in a small saucepan over low heat, stirring frequently until smooth and melted. Pour the chocolate-peanut butter mixture over the first oat layer in the pan, and spread evenly with a knife or the back of a spoon. Top with the remaining oat mixture, and then top with remaining chocolate chips and peanut butter chips.

Cool the bars in the fridge for 2-3 hours before serving. Store the bars in the fridge for best results!