To make the muffins:
Preheat oven to 350 degrees F. Spray 12-muffin muffin pan with cooking spray.
Combine flour, oats, baking powder, baking soda, and salt, in large bowl, mixing to combine.
In separate bowl, whisk together melted butter, yogurt, maple syrup, vanilla, lemon zest, and eggs.
Pour into dry ingredients and stir with a spatula until combined. Don't over mix.
Fold in blueberries.
Pour into prepared muffin pan.
Combine all crumb topping ingredients in a small bowl, stirring to combine.
Sprinkle over muffins.
Bake in preheated oven for 18-22 minutes, until tops are golden brown and tester comes out clean.
Enjoy!