Place 8 cups of Rice Chex cereal into a large mixing bowl and set aside.
Combine 1 cup chocolate chips, 1/2 cup creamy peanut butter, and 4 tablespoons unsalted butter in a medium microwave-safe bowl.
Microwave the chocolate mixture in 30-second intervals, stirring between each, until smooth and fully combined.
Stir 1 teaspoon vanilla extract into the melted chocolate-peanut butter mixture.
Pour the warm chocolate mixture over the cereal and gently stir with a spatula until the cereal is evenly coated.
Place 1 1/2 cups powdered sugar into a gallon-sized resealable bag, add the coated cereal, seal the bag, and shake until all pieces are well coated in powdered sugar.
Transfer the coated cereal to a baking sheet or bowl to cool and set, then serve.