Combine first 3 ingredients in a glass bowl; microwave at HIGH 3 to 4 minutes or until melted, stirring once. Stir in vanilla.
Fold in 6 cups cereal and peanuts. Spread mixture into a lightly greased 13- x 9-inch pan. Cover and chill 1 hour or until set; cut into small squares.
Prep: 10 min., Chill: 1 hr.