Heat the oven to 350°F. Grease a 9x5-inch loaf pan or line it with parchment paper.
In a large bowl, mash the bananas until smooth, then whisk in the eggs, Greek yogurt, honey, olive oil and vanilla until well combined.
Add the flour, oats, baking soda, cinnamon and salt. Fold with a spatula until just combined, then fold in the walnuts. Do not overmix.
Pour the batter into the pan and sprinkle 1 tablespoon of oats over the top.
Bake for 50 to 55 minutes, until a toothpick inserted in the center comes out clean and the top springs back when lightly pressed.
Cool in the pan for 15 minutes, then turn the loaf out onto a wire rack. Cool completely before slicing into 12 slices.