Preheat oven to 375°F. Line a 13x9-inch pan with foil; spray foil with nonstick spray.
In a medium saucepan, stir the brown sugar, butter and corn syrup over medium heat until combined. Remove from heat and stir in the peanut butter and vanilla; stir until smooth.
Place the oats in a very large bowl. Pour the brown sugar mixture over the oats; stir to combine. Press the oat mixture onto the bottom of the prepared pan.
Bake 10 to 12 minutes, until golden. Don’t over-bake (you don’t want it to brown) or it will be on the crunchy side. Let the cookie layer cool for about 15 minutes on a wire rack.
ADD THE CANDY LAYER AND TOPPINGS:
In the same saucepan, stir the chips and peanut butter over low heat until melted and smooth.
Sprinkle ½ cup of chopped peanuts over the baked cookie layer. Pour the chocolate over the peanuts; spread to make an even layer. Sprinkle the chocolate and peanut butter chips and remaining peanuts over the top; press lightly into the chocolate layer.