2Place popcorn in a large pot with 2 tablespoons vegetable oil. Over a low heat, begin to pop the popcorn. Constantly shake the pot to ensure that the popcorn kernels and oil do not burn. Once the popping has slowed, remove the pot from heat.
3In a large saucepan, mix butter or margarine, brown sugar and corn syrup. Bring this mixture to a boil (over a medium heat) while stirring constantly. Reduce heat to medium-low and do not stir for 5 minutes. Remove the pan from heat and mix in baking powder and vanilla extract, stirring carefully.
4In a large baking pan, combine popcorn, pretzels, cereal and pecans. Pour the butter mixture over the popcorn mixture, stir to coat.
5Bake for 30 minutes, stirring the mixture after the first 15 minutes have elapsed.