Preheat & Prep. To start, preheat the oven to 350 degrees F. Grease a 2-quart baking dish or 9x9 pan.
Combine Dry Ingredients. In a large bowl, whisk together the oats, baking powder, salt, cinnamon, nutmeg, and cardamom. Add 1/2-3/4 cup of the pecans (and save the rest for sprinkling on top).
Combine Wet Ingredients. In a medium bow, whisk together the wet ingredients--milk, pumpkin, syrup, chia egg/egg, and vanilla. Whisk until well combined.
Stir the wet ingredients into the dry oatmeal mixture. Stir to combine well. Pour into a greased 2-quart casserole dish or baking pan. Sprinkle with additional pecans if you like.
Bake at 350 degrees 25-30 minutes, or until the liquid has soaked in, the center is just set, and the edges are starting to turn golden.
Serve with a drizzle of milk and a little extra maple syrup, a splash of milk, or a dollop of greek yogurt, if you like! Cover leftover oatmeal with aluminum foil or plastic wrap or an airtight container and store in the refrigerator up to 3-4 days. To reheat, simply add a little extra milk and warm in the oven or microwave.