Grease roasting pan with vegetable spray.
Put popped corn into roasting pan.
Mix brown sugar, margarine,vanilla and corn syrup. Boil 5 minutes, stirring occasionally.
Remove syrup from heat and stir in peanuts.
Add baking soda quickly, until it foams.
Pour syrup over popcorn, mixing well.
Bake at 250º for 1 hour, stirring every 15-20 minutes. Make sure mixture does not stick to bottom of pa.
Cool. Store in tightly closed container.