Heat oven to 400ºF. Line 12 medium muffin cups with paper baking cups. In large bowl, combine flour, oats, sugar and baking powder; mix well. In small bowl, combine milk, oil, egg and vanilla; blend well. Add to dry ingredients all at once; stir just until dry ingredients are moistened. (Do not overmix.) Gently stir in blueberries and strawberries. Fill muffin cups three-fourths full. Sprinkle batter in each muffin cup with 1 teaspoon cinnamon-sugar. Bake 18 to 20 minutes or until golden brown. Cool muffins in pan on wire rack 5 minutes; remove from pan. Serve warm.