Heat oven to 250° F. Spray 13 x 9-inch baking pan with cooking spray.
Place cereal in pan.
Place butter in 2-cup microwaveable bowl. Microwave on HIGH 45 seconds or until melted. Stir in sugar, syrup and vanilla; mix well. Pour over cereal; stir to coat evenly.
Bake 1 hour, stirring every 15 minutes. Remove from oven; stir in caramel corn.
Transfer to baking sheet, spreading mixture in even layer. Cool completely. Store tightly covered at room temperature.
Servings: 12 cups