Preheat oven to 350 degrees. Line a bread loaf pan with parchment paper, or spray very well with non-stick spray. Set aside.
In a large bowl mix together yogurt, mashed bananas, eggs, vanilla and brown sugar.
In a separate bowl whisk together cocoa powder, flour, baking powder, salt, and baking soda. Slowly add to the yogurt mixture, mixing until just combined.
Fold in the oats.
Add chocolate to the batter, reserving about 2 Tbls to sprinkle on top, stir until just combined.
Pour batter into prepared pan. Sprinkle remaining chocolate over the top.
Bake for 45-60 minutes until a tester comes out clean.
Remove and place on a wire rack for 10 minutes before removing from pan.
Let cool completely before slicing.