Heat oven to 400°F Spray bottoms only of mini muffin pan cups with cooking spray.
For topping, combine sugar and cinnamon in small bowl; mix well and set aside.
For muffins, combine flour, oats, sugar and baking powder in large bowl; mix well. In small bowl, combine milk, egg, margarine and vanilla; blend well. Add to dry ingredients all at once; stir just until dry ingredients are moistened. (Do not overmix.)
Fill muffin cups two-thirds full. Sprinkle topping evenly over tops of muffins.
Bake 12 to 14 minutes or until light golden brown. Cool muffins in pan on wire rack 5 minutes; remove from pan. Serve warm.
Note: To prepare regular-size muffins, line 12 medium muffin pan cups with paper baking cups or spray bottoms only with cooking spray. Prepare muffin batter as directed above. Fill muffin cups almost full. Sprinkle with topping. Bake 18 to 22 minutes or until light golden brown. Cool muffins in pan on wire rack 5 minutes; remove from pan. Serve warm.