This muffin is so delicious and moist, its one of our top 5 favorite recipes in the issue. The batter fills the muffin cups more than most recipes, but it wont overflow when baked.
Preheat oven to 400F. Coat 12 standard muffin pan cups with cooking spray.
Place diced apple on paper towels to drain; pat dry. Combine flour, oats, sugar, baking powder, baking soda, salt and cinnamon in medium bowl, and stir with whisk. Combine yogurt, milk, oil, vanilla and egg in small bowl and stir to blend. Make well in center of flour mixture; add milk mixture, stirring just until moist. Mix in apple.
Divide batter evenly among prepared cups. Bake 20 minutes, or until muffins spring back when pressed lightly in center. Remove from pan, and cool on wire rack.