In large microwavable bowl, microwave baking chips uncovered on High 1 minute 30 seconds to 2 minutes 30 seconds, stirring every 30 seconds, until melted and smooth. Stir in oil.
Gently stir in cereal until evenly coated.
Spread on waxed paper or foil; top with Halloween sprinkles. Cool until chocolate is set, about 30 minutes. Break into chunks. Store loosely covered.