Spray the bottom and sides of a 13x9-inch pan with cooking spray. Spray large bowl with non-stick cooking spray. Place cereal in bowl and set aside.

Spray medium microwavable bowl with cooking spray; add caramels and water. Microwave uncovered on High 2 minutes to 2 minutes 30 seconds, stirring after each minute, until mixture is smooth. Remove from microwave. Mix in marshmallows until melted and smooth.

Pour the caramel mixture over cereal in bowl; stir until cereal is evenly coated. Pour cereal mixture into the prepared 9 x 13 pan. With back of spatula sprayed with cooking spray, press mixture in pan until even.

In small microwavable bowl, add in baking chips and oil. Microwave uncovered on High 1 minute to 1 minute 30 seconds, stirring after 1 minute, until mixture is smooth. Drizzle melted mixture over top of cereal mixture. Refrigerate until mixture is firm and chocolate is set, about 30 minutes.