Preheat oven to 350F. Lightly grease a 9x13 baking pan and set aside. In a large bowl, beat sugar and butter until smooth and creamy. Beat in yogurt, mashed banana, eggs, milk, and vanilla until smooth.
In a separate bowl, combine flour, baking soda, baking powder, and salt. Gently fold flour mixture into liquid until batter is smooth. Fold in blueberries. Scrape batter into prepared pan and set aside for a moment.
Make the topping: In a small bowl, combine all topping ingredients until crumbly. Sprinkle evenly over coffee cake batter.
Bake coffee cake at 350F 50-55 minutes or until a toothpick inserted in center comes out clean. Cool coffee cake 10 minutes, before slicing into squares and serving warm. Enjoy!