Preheat the oven to 350 degrees.
In a large bowl add all ingredients except the pecans, greek yogurt, and a handful of the cubed apples. Give it a good mix so that the eggs are well incorporated.
Let it sit for about 5 minutes while you prepare the baking dish.
Add some parchment paper to the bottom of a medium-sized baking dish. If you don't have parchment paper just make sure to grease the dish.
Add the oatmeal mixture to the baking dish and spread evenly. Top with the rest of the apples, chopped pecans if using and a little sprinkle of cinnamon.
Place in the oven for 35-40 minutes or until fully cooked through. Keep an eye on it and make sure not to overbake, otherwise, it will become too crumbly.
Once baked, remove from the oven and allow to cool before cutting it into your preferred serving size. Store in an airtight container in the fridge and serve with some greek yogurt!