Arrange graham crackers to cover the entire bottom of a 15x10 inch pan. Sprinkle marshmallows, chocolate chips, and peanuts over the graham crackers.
In a small saucepan, cook the butter and brown sugar until dissolved. Remove from heat and add vanilla. Pour evenly over the ingredients in the pan. Bake for 10 to 12 minutes in the preheated oven. Store in the refrigerator for 3 days or the freezer for 1 month.