Preheat your oven to 350°F (175°C) and grease a 9x5-inch loaf pan or line it with parchment paper.
In a large mixing bowl, combine the mashed bananas, Greek yogurt, honey (or maple syrup), eggs, and vanilla extract. Mix until well combined.
In another bowl, whisk together the whole wheat flour, rolled oats, cocoa powder, baking soda, and salt.
Gradually add the dry ingredients to the wet ingredients, stirring until just combined. Be careful not to overmix.
If desired, fold in the chocolate chips and chopped nuts.
Pour the batter into the prepared loaf pan and smooth the top with a spatula.
Bake for 50-60 minutes, or until a toothpick inserted into the center comes out clean.
Allow the bread to cool in the pan for 10 minutes before transferring it to a wire rack to cool completely.