PREP: Line a 9x13-inch pan with parchment paper (not foil). Lightly grease with cooking spray and set aside. Preheat the oven to 350 degrees F.
BROWNIES: In a large bowl, prepare the brownies according to package instructions. Bake for 21 minutes at 350 degrees F. They won't be fully cooked through at this point; don't worry--they go back in the oven!
CARAMEL LAYER: While the brownies are baking, combine the unwrapped caramels and heavy whipping cream in a medium-sized pot over medium-low heat. Gently stir until melted and smooth, about 5-8 minutes. Once smooth, remove from heat and set aside.
ADD CHOCOLATE CHIPS: As soon as the brownies are out of the oven, sprinkle the chocolate chips right on top. Immediately pour and gently spread the caramel layer on top.
OATMEAL COOKIE LAYER: Melt the butter and then allow to cool back to room temperature. Do not add hot butter to this mixture; it will make it all greasy! In another large bowl, combine the flour, oats, brown sugar, baking soda, and salt. Once the butter has cooled, add it into the mixture. Mix with a wooden spoon or a hand mixer until you have a thick, crumbly oatmeal mixture.
BAKE BARS AGAIN: Crumble the cookie mixture evenly over the melted caramel and bake for another 13-16 minutes or until golden brown on top.
ENJOY: Remove from the oven and allow bars to cool and set up for at least 1 hour before cutting into the bars. Store leftover bars in an airtight container at room temperature. Bars are best enjoyed within 2-3 days.