Preheat oven to 350°F. In a large bowl, combine oats, brown sugar, flour, baking powder, and baking soda.
Cut in butter using a pastry blender or two knives until the mixture resembles fine crumbs. Stir in peanuts.
Reserve 1 1/2 cups of the crumb mixture. Stir the egg into the remaining mixture and press it into the bottom of a 13×9-inch baking pan.
Bake for 15 minutes.
In a small bowl, stir together sweetened condensed milk and peanut butter until smooth. Pour this mixture over the partially baked crust.
Sprinkle the reserved crumb mixture and chocolate chips evenly over the peanut butter layer.
Bake for another 15 minutes. Let cool before cutting into bars.