Grease jelly-roll pan, 15x10". Grease large bowl. Mix cereal, peanuts, and raisins in bowl. Heat oven to 250~. Heat brown sugar, margarine, corn syrup and salt in a 2-qt saucepan over medium heat, stirring constantly, until bubbly around edges. Cook uncovered for 2 minutes, stirring occasionally; remove from heat. Stir in baking soda until foamy and light colored. Pour over cereal mix; stir until mix is coated. Spread evenly in pan. Bake 15 minutes; stir. Let stand about 10 minutes or just until cool. Loosen mix with a metal spatula. Let stand about 30 minutes or until firm. Break into bite-sized pieces.