Preheat oven to 400°F. Spray a 12-hole muffin pan with cooking spray.
Stir together flour, oats, brown sugar, macadamia nuts, baking powder, baking soda, cinnamon and salt in a large bowl.
Puree mango in a blender until smooth. Add oil, egg, vanilla and orange peel and blend. Add mango mixture to dry ingredients and stir just until moistened.
Spoon evenly into prepared muffin cups. Bake for 15 to 20 minutes, or until toothpick inserted in center comes out clean.
Cool 5 minutes; remove from pan and serve warm.