Sift together flour, baking powder, salt and sugar into bowl. Stir in oats. Add remaining ingredients; stir only until dry ingredients are moistened. Fill greased medium-sized muffin cups 2/3 full. Bake in preheated hot oven (425 F.) about 15 minutes. Serve piping hot. FRUIT OR NUT MUFFINS: Add 1/2 cup raisins, chopped pitted dates or nutmeats with the oats. CINNAMON-TOPPED MUFFINS: Combine 2 tablespoons sugar, 2 teaspoons all-purpose flour, 1 teaspoon cinnamon and 1 teaspoon melted butter or margarine. Sprinkle over muffins before baking.