Chop or break up oreos in a ziplock bag before you begin.
Melt butter in a large non-stick pan. Add marshmallows & stir until everything is melted.
Remove from heat & add rice cereal. Add ¾ of the cookie crumb mixture. Stir well & spread into a greased 9x13" pan. Pat down with hands or spatula.
Put chocolate chips in a glass dish & heat in the microwave on 50% power for 30 seconds at a time, stirring before each additional 30 seconds. Continue until melted. Spread over the top of the rice krispy treats & immediately press the remaining chopped oreos over the top.