Rice Krispie Squares

1/4 cup margarine
40 large marshmallows or 5 cups mini marshmallows
1/2 tsp vanilla
6 cups Rice Krispies cereal

Melt the margarine in the microwave. Add the marshmallows, microwave 2 minutes at a time and stir until melted and smooth. Add the vanilla and the cereal, stir until coated. Press into a 9x13 pan and cool.