Preheat your oven to 350°F and adjust the rack to the center position. Lightly butter an 8-inch or 2-quart baking dish to ensure easy release.

In a mixing bowl, whisk together the rolled oats, brown sugar, baking powder, cinnamon, nutmeg, salt, and ¼ cup of the chopped pecans. Stir the mixture thoroughly to evenly distribute the dry ingredients.

In a separate bowl, crack the eggs and beat them with a whisk until fully combined. Pour in the milk and vanilla extract, whisking vigorously until smooth. Gradually stir the melted butter into the liquid mixture.

Take the prepared baking dish and evenly layer 2 cups of blueberries across the base. Carefully pour the oat mixture over the berries, ensuring an even spread. Use a spatula to smooth out the surface if necessary.

Top the oatmeal mixture with the remaining ½ cup blueberries and ¾ cup pecans, scattering them evenly to create a crunchy, fruit-studded topping.

Transfer the dish to the oven and bake for 45 to 55 minutes, or until the oats are firm and the pecans have turned a deep, golden-brown hue. Remove from the oven and allow the oatmeal to cool for at least 5 minutes.

Serve warm or at room temperature. For added creaminess and a touch of indulgence, pair it with lightly sweetened Greek yogurt, if desired.