Creating your own Blueberry Coffee Cake is simple with these easy steps:

1. Preheat the Oven: Preheat your oven to 350°F (175°C). Grease and flour a 9×13-inch baking pan.

2. Mix Dry Ingredients: In a large bowl, combine the flour, granulated sugar, baking powder, baking soda, and salt. Whisk these dry ingredients together until well combined.

3. Add Butter: Add the softened butter to the dry mixture. Use a pastry cutter or your fingers to mix until it resembles coarse crumbs.

4. Combine Wet Ingredients: In another bowl, whisk together the sour cream, eggs, and vanilla extract until smooth.

5. Combine Mixtures: Pour the wet ingredients into the dry mixture. Stir gently until just combined; do not overmix.

6. Fold in Blueberries: Gently fold in the fresh blueberries until evenly distributed throughout the batter.

7. Prepare Streusel Topping: In a small bowl, mix together the brown sugar, rolled oats, cinnamon, and melted butter until crumbly.

8. Pour Batter into Pan: Spread the batter evenly into the prepared baking pan.

9. Add Streusel: Sprinkle the streusel mixture generously over the cake batter.

10. Bake: Place the pan in your preheated oven and bake for 40-45 minutes, or until a toothpick inserted in the center comes out clean.

11. Cool: Once baked, remove from the oven and allow the cake to cool in the pan for about 15-20 minutes before slicing.