My Grandmother was the best cook in the whole world. When she prepared food, which was all of the time, she did it with the grace of God. Her measurements were exact, a handfull of this and two of that. This is passed down through cyberspace from her to you.
This recipe makes a 18 inch by 26 inch bake sheet or about 40 good size squares. It can be scaled down quite nicely for any amount.
Melt the margarine over low heat. Add the marshmallows and cook until melted. Remove from the heat. Add vanilla and cereal and stir until coated. Press warm mixture firmly onto bake sheet. Cool and cut into squares.