Instructions

• Preheat the oven to 350°F. If you are using unsalted butter, either add 1/4 teaspoon salt to the graham cracker crumbs now or plan to sprinkle salt on the bars after they bake.
• Line a 9x13-inch baking dish with parchment paper and spray the parchment with cooking spray.
• Place 1/2 cup salted butter in a microwave-safe bowl and heat 30–60 seconds, or until fully melted.
• In a medium bowl, combine the melted butter with 1 1/2 cups graham cracker crumbs until the crumbs are evenly moistened.
• Press the graham-butter mixture evenly and firmly into the bottom of the prepared 9x13 pan to form the crust.
• Evenly pour the 114 ounce can sweetened condensed milk over the graham cracker crust.
• Sprinkle the old fashioned oats, peanut butter chips, chocolate chips, and mini M&Ms evenly over the sweetened condensed milk. Gently press the toppings down just enough to help them adhere to the condensed milk.
• Bake at 350°F for 20–25 minutes, or until the edges are golden and the toppings look set.
• Remove from the oven and cool completely in the pan on a wire rack before slicing into squares. If you used unsalted butter and did not add salt earlier, sprinkle a little salt on top now if desired.