In large mixing bowl measure our 8 cups of Rice Chex cereal (slightly less than a 12 oz. box). Set aside.
In microwave-safe bowl add chocolate chips, peanut butter, and butter and microwave for 1 minute. Stir and return to microwave for 30 more seconds. Stir and add vanilla.
Pour chocolate mixture on top of chex cereal and gently toss until cereal is covered in chocolate.
Add powdered sugar and toss to combine. You can also put the mixture into a large ziptop bag and gently shake until all of the cereal is coated.