1. In large saucepan over low heat, melt butter. Add marshmallows and peanut butter; stir until melted and well blended. Remove from heat.
2. Stir in vanilla. Add cereal, stirring until coated.
3. Using lightly-buttered spatula, press mixture firmly and evenly into buttered 3.5 L (13 x 9") pan. Cool about 10 minutes. Cut into squares.
In keeping with good allergy practices, we remind you to be aware of allergens and to check labels on any packaged goods used. This recipe has been tested using Kellogg's* products. Results with other products may vary.