Add 6 cups of rice krispie cereal slowly to your marshmallow mixture.
Once the cereal and marshmallows are totally combined, add 1 cup of Reeses Pieces. Stir in well.Note: you don't want the marshmallows totally cooled, but make sure they aren't so hot they will melt the candies. Take greased pan and add cereal, candy and marshmallow mixture to it.
Gently press the treats into the pan, being careful not to crush your candy.
Allow the treats to cool - about 30 minutes.
Using a knife, cut your treats into 16 even bars.