Preheat oven to 350℉.
Cream the butter, brown sugar and white sugar until light and fluffy.
1/2 cup butter, 1/2 cup brown sugar, 1/2 cup sugar
Beat in the egg, peanut butter, baking soda, salt and vanilla.
1 egg, 1/3 cup peanut butter, 1/2 teaspoon baking soda, 1/2 teaspoon salt, 1/2 teaspoon vanilla
Stir in the flour and oatmeal and press into a greased 9x13 pan and bake for 18-20 minutes. Do NOT overbake.
1 cup flour, 1 cup quick oats
Remove from the oven and immediately sprinkle chocolate chips on top. Let sit for 3-5 minutes or until the chips are melted.
1 cup semi-sweet chocolate chips
Spread the melted chips across the bars; cool completely. (Refrigerate to speed this up if you're in a hurry!)
Combine the powdered sugar, peanut butter and 1 tbsp milk. Add additional milk, if needed and spread over cooled bars.
1/2 cup powdered sugar, 1/4 cup peanut butter, 1-2 tablespoons milk