Heat oven to 250º F. Spray 13 x 9-inch baking pan with cooking spray.
Combine cereal and pecans in pan; mix well. In large microwaveable bowl, combine sugar, corn syrup and butter. Microwave on HIGH 1 minute 30 seconds; stir. Microwave an additional 30 seconds to 1 minute 30 seconds or until boiling.
Stir vanilla and baking soda into sugar mixture. Pour over cereal mixture; stir to coat evenly.
Bake 1 hour, stirring every 15 minutes. Transfer to baking sheet, spreading mixture in even layer. Cool completely; break into pieces. Store tightly covered at room temperature.
Servings: 10 cups