1Heat oven to 250ºF. Spray 15x10-inch pan or large cookie sheet with cooking spray. In large bowl, place cereal; set aside.
2In small microwavable bowl, microwave chocolate chips and butter uncovered on High 30 seconds; stir. Continue to microwave in 30-second increments until mixture can be stirred smooth.
3Drizzle mixture over cereal; toss until well coated. Sprinkle dry brownie mix and candy sprinkles over cereal; toss until well coated. Spread in single layer in pan.
4Bake uncovered 30 minutes, stirring after 15 minutes. Cool about 15 minutes. Store tightly covered at room temperature.