Heat oven to 350 degrees. Spray 13 x 9-inch pan with cooking spray.
Combine brown sugar and butter; beat until smooth. Stir in oats and cereal. Add flour, baking soda and salt; mix until well blended. Reserve 1 cup of mixture for topping; set aside.
Press remaining mix into bottom of pan. Bake at 350 degrees for 10 minutes.
Meanwhile, in small pan on stove, heat caramels and milk over low heat, stirring constantly until melted and smooth.
Remove partially baked crust from oven. Sprinkle with 1 cup of candy-coated chocolate pieces. Drizzle with melted caramel, avoiding the sides of pan.Drop reserved oat mixture by heaping spoonfuls over the top. Sprinkle with remaining chocolate pieces.
Return to oven. Bake 20-25 minutes or until center is set and top is golden brown. Cool 1 hour.