Preheat & Prep. To start, preheat the oven to 350 degrees F. Grease a 2-quart baking dish (like an 8×8 or 9×9″ pan).
Combine Dry Ingredients. In a large bowl, combine oats, baking powder, cinnamon, and salt. Stir to combine.
Add Wet Ingredients. Pour in milk, syrup, egg or chia egg, melted butter/oil, and vanilla. Stir to combine. Pour oatmeal mixture into your prepared baking dish.
Make Pecan Topping. In a small saucepan on the stovetop (or in a microwave-safe bowl), melt together 2 Tbsp. butter and 1/4 cup syrup. Add the pecans and stir to coat. Pour the pecan mixture over the oatmeal mixture and smooth out with your spatula.
Bake Oatmeal. Then, bake at 350 degrees for 35-40 minutes, or until the oatmeal has plumped and the top is golden. Remove from the oven and let stand about 5 minutes before scooping or slicing.
Serve & Store. Enjoy right away or cover and refrigerate 2-3 days. To reheat, you can pop this back into the oven at 350 degrees for about 10 minutes, or you can simply microwave a few seconds to warm up. (I like to add a splash of milk when reheating.)