1. Mix cereal and popcorn in a large microwave bowl and set aside. (Note: You may use a combination of Rice, Corn or mixed Chex, if desired.)
2. Microwave margarine, sugar, corn syrup and vanilla in large bowl on high for 2 minutes, or until boiling. Make sure to stir after 1 minute.
3. Pour margarine mixture over cereal mixture until evenly coated. Microwave for 5 to 6 minutes, stirring and scraping the sides of the bowl after every minute.
4. Spread mixture on wax paper to cool, stirring occasionally to break it up. Store in an airtight container.

Yields about 1/2 cup per serving.