Preheat your oven to 350°F (175°C) and grease a 9x9-inch baking dish or an equivalent-sized pan.

In a large bowl, mix together the rolled oats, cocoa powder, baking powder, and salt until evenly combined.

In a separate bowl, whisk together the maple syrup, eggs, milk, vanilla extract, and melted coconut oil.

Pour the wet ingredients into the dry ingredients and stir until fully incorporated.

Fold in the chocolate chips if using, ensuring they are evenly distributed.

Transfer the mixture to the prepared baking dish and spread it out evenly.

Bake in the preheated oven for 30-35 minutes, or until the top is set and a toothpick inserted into the center comes out mostly clean.

Allow the baked oatmeal to cool for 5-10 minutes before slicing into squares or scooping into bowls. Serve warm or at room temperature.