Preheat the Oven and Prepare the Muffin Pan

• Preheat your oven to 400 degrees Fahrenheit (204 degrees Celsius).
• Grease a 12-cup muffin tin or line it with muffin papers.

Combine Dry Ingredients

• In a large mixing bowl, whisk together the flour, rolled oats, sugar, salt, and baking powder. If you chose to add cinnamon or lemon zest, mix them in now.

Mix Wet Ingredients

• In another bowl, beat the milk, egg, melted butter, and vanilla extract until just combined.

Combine Wet and Dry Mixtures

• Pour the wet ingredients into the dry ingredients. Stir using a spatula until just combined. The batter should be lumpy and not overly smooth.

Add Blueberries

• Gently fold the blueberries into the batter, being careful not to overmix to prevent the muffins from becoming tough.

Prepare the Topping

• In a small bowl, mix the oats, brown sugar, and cinnamon for the topping.

Fill the Muffin Cups and Add Topping

• Spoon the muffin batter into the prepared muffin tin, filling each cup about 3/4 full.
• Sprinkle each muffin with the prepared topping mixture.

Bake the Muffins

• Bake in the preheated oven for 20-25 minutes, or until the tops are golden brown and a toothpick inserted into the center of a muffin comes out clean.

Cool and Serve

• Allow the muffins to cool in the pan for 5 minutes before transferring them to a wire rack to cool completely.
• Enjoy your blueberry oatmeal muffins warm or at room temperature!