Pour your 5 cups of Cheerios into a large bowl. Set aside.
Place the butter and marshmallows in a large sauce pan over medium heat. Stir continuously while heating, until melted and smooth.
Add the peanut butter and stir until blended.
Pour mixture over Cheerios, fold in until all pieces are covered.
Add chocolate chips, and distribute evenly throughout.
Pour into a lightly greased 13 x 9 pan and press into place.
Add sprinkles if desired.
Cool slightly before serving.