MICROWAVE semi-sweet chocolate and 8 oz. white chocolate in large microwaveable bowl on HIGH 2 min.; stir. Microwave 1 to 2 min. or until chocolates are completely melted and mixture is well blended, stirring every 30 sec. Add marshmallows, cereal and nuts; mix well.
SPREAD onto bottom of 12-inch pizza pan sprayed with cooking spray; top with cherries and coconut.
MICROWAVE remaining white chocolate and oil in small microwaveable bowl on HIGH 1 min.; stir. Microwave 30 sec. to 1 min. or until chocolate is completely melted and mixture is well blended, stirring every 15 sec. Drizzle over coconut; let stand until firm.