Grease a 9×9 inch pan and set aside. In a medium pot, melt butter. Stir in brown sugar and vanilla. Add oats and cook on low for a few minutes.
Pour half the mixture into the greased pan and press down with a spatula. Set aside reserve.
In another pot, melt chocolate chips and peanut butter on low. Stir until smooth and pour over the oat layer.
Crumble the remaining oat mixture over the chocolate layer, pressing in gently.
Melt chocolate chips and drizzle over top.
Cover, and refrigerate for a few hours. Bring bars to room temp before cutting