Preheat oven to 350°F. Place cupcake liners in a muffin pan.
Mix dry ingredients together in a large bowl; set aside.
Mash bananas with a fork and heat oil just until melted (be careful not to over-heat).
In a separate bowl, combine the eggs, oil, yogurt, and banana.
Add wet ingredients to the dry ingredients and stir just until moistened. Evenly distribute batter into muffin cups.
Combine the coconut and walnuts in a small bowl, then sprinkle over each muffin.
Bake for 15-20 minutes until a toothpick inserted into the center of a muffin comes out clean.