Preheat the oven to 350 degrees F. Grease and flour a muffin tin and set aside. Do not use muffin liners as these muffins will stick to the liners.
In a large bowl, beat together the Greek yogurt and the bananas. Make sure your bananas were ripe and are well mashed to avoid large banana chunks. Beat in the eggs, vanilla extract, and brown sugar.
Meanwhile in a blender or food processor blend quick oats or old fashioned oats to form a flour consistency. Make sure to measure the oat flour AFTER it has been blended and not before.
In a separate bowl, stir together the oat flour, the quick oats (MUST be quick oats not steel cut or old fashioned), cinnamon, baking soda, baking powder, and salt.
Combine the wet and dry ingredients and stir until just combined. Over mixing will result in dense muffins. Stir in the chocolate chips.
Divide the batter among the 12 muffin cavities. These muffins don't rise too much so use all the batter in the 12 cavities.
Bake for 17-20 minutes. Remove and allow to slightly cool and then pull them out of the muffin pan onto a cooling rack to finish cooling.
Store these muffins in an airtight container or bag in the fridge (warm in the microwave before eating) and enjoy or freeze within 3 days.
Notes
*I recommend a high quality 2% fat content vanilla Greek yogurt for optimal results on these muffins. **Increase the brown sugar if you aren't "used" to healthier snacks/breakfasts going to 6-7 tablespoons.