Preheat the oven to 375° F. Grease an 8X8-inch baking dish and set aside.
Toss the oats, chopped pecans, ground cinnamon, salt, and baking powder in a small bowl.
Mash the bananas. Add the avocado oil, eggs, milk, vanilla extract, and maple syrup. Mix until smooth and well incorporated. Add the oat mixture and mix until everything is combined.
Pour the custard into the prepared dish and bake for 35-40 minutes or until set and golden brown. If you like your baked oatmeal a little more on the firm side, like me (and as pictured), bake for a little longer.
Allow the baked oatmeal to cool before slicing it into 6 squares. Store in an airtight container in the refrigerator for up to 4 days, or freeze for up to 3 months.