In a microwave or in a large saucepan over low heat, melt marshmallows and oil; stir until smooth. Remove from heat; stir in cereal and 1 cup chopped Oreos. Press mixture into a lightly-greased 13x9-in. baking pan using wax paper or a lightly-greased spatula. Cool to room temperature. Spread melted white baking chips on top; sprinkle with remaining 1 cup chopped Oreos. Cut into bars.