Stir together the flour, baking powder, salt and sugar in a large bowl. Make a well in the center. In a small bowl or 2 cup measuring cup, beat egg with a fork. Stir in milk and oil. Pour all at once into the well in the flour mixture. Mix quickly and lightly with a fork until moistened, but do not beat. The batter will be lumpy. Pour the batter into paper lined muffin pan cups.
Variations: Blueberry Muffins: Add 1 cup fresh blueberries. Raisin Muffins: Add 1 cup finely chopped raisins. Date Muffins: Add 1 cup finely chopped dates. Cheese Muffins: Fold in 1 cup grated sharp yellow cheese. Bacon Muffins: Fold 1/4 cup crisp cooked bacon, broken into bits.