Mix oil, brown sugar, egg, milk, peanut butter and vanilla in an electric mixer till well combined.
Add remaining ingredients, except chocolate chips and mix well.
Mix in chocolate chips.
Press into greased 9 x 13 or 10 x 15 pan. The size pan will determine the thickness of the bars, but either size will work.
Bake 20 minutes at 350° or until a toothpick comes out clean.
Cool and cut into bars.
Wrap in plastic wrap and store in freezer.