Preheat oven to 400°F Line twelve muffin cups with paper baking cups or lightly oil bottoms only.
Prepare topping. Mix oats, brown sugar, and cinnamon together. Add melted butter and mix well.
Prepare muffins. Mix oats, flour, baking powder and soda, and cinnamon in a bowl. In separate bowl, mix applesauce, milk, brown sugar, oil, and egg. Add to dry ingredients and stir just until dry ingredients are moistened.
Fill cups with mix (fills to about 3/4 full), and top each muffin with topping. Then bake 18-20 minutes. Serve warm if possible. Yum! Simple and delicious.