Preheat the oven to 350°F (175°C).

In a large bowl, combine the rolled oats, baking powder, cinnamon, nutmeg, and optional chopped nuts.

In a separate bowl, whisk together the grated carrots, Greek yogurt, honey or maple syrup, and eggs until well combined.

Pour the wet mixture into the dry ingredients and stir until just combined.

Grease a baking dish with cooking spray or oil, then transfer the oatmeal mixture into the dish, spreading it evenly.

Bake in the preheated oven for about 30-35 minutes, or until the edges are lightly golden and a toothpick inserted in the center comes out clean.

Allow the baked oatmeal to cool for a few minutes before slicing into squares or scooping out portions.