Preheat the oven to 300 degrees. In a super large bowl, mix together all the dry ingredients, except the raisins. Pour in the melted butter and the vanilla and continue to stir until everything is well blended. Transfer the granola onto two large cookie sheets or shallow baking pans and spread evenly. Toast for 45 minutes, stirring every 15 minutes. Turn off the oven and let the granola cool in the oven with the door open. When cool, stir in the raisins, then put in an airtight container to store.
Makes about 18 cups