Place Rice Chex cereal in a large mixing bowl and set aside.
In a microwave-safe bowl, combine chocolate chips, peanut butter, and melted butter. Microwave in 30-second intervals, stirring after each, until smooth.
Stir vanilla extract into the melted chocolate mixture.
Pour the chocolate mixture over the cereal and gently stir until the cereal is evenly coated.
Transfer the coated cereal into a large resealable plastic bag. Add powdered sugar, seal the bag, and shake until all pieces are coated.
Spread the Puppy Chow bites on wax paper to cool and set before serving.
Notes
Store Puppy Chow bites in an airtight container at room temperature for up to one week for best freshness.