Preheat oven to 350F. Line 2 large sheet pans with parchment paper and set aside.
In a large bowl, beat mashed banana, brown sugar, egg, yogurt, coconut oil and vanilla until smooth.
In a separate large bowl, combine flour, oats, baking powder, baking soda, cinnamon, and salt. Fold flour mixture into liquid until dough is just combined (dough will be slightly sticky). Fold in chocolate chunks.
Scoop dough into 2-inch balls, drop 2 inches apart on prepared sheet pans and flatten slightly. Bake cookies at 350F 10-12 minutes until edges of cookies are golden brown (center will still be slightly soft in the center).
Allow cookies to cool on pans 10 minutes then transfer to a wire cooling rack. Enjoy!