Liberally mist a 9- × 13-inch casserole dish with oil spray.
Add bananas and mash. Add Greek yogurt, milk, vanilla, maple syrup (or honey) and eggs (you can crack eggs right into casserole dish but be sure to whip them with a fork before mixing into the entire wet batter).
Mix and mash all wet ingredients together until it’s as smooth as possible; you will most likely still have lumps throughout—that’s fine.
Add oats, cocoa powder, baking powder, salt, and mix until well combined (ensuring dry cocoa powder is completely incorporated into batter). Mix in chocolate chips. Add optional extra chips over the top. Bake about 50 minutes.
Slice into 9 squares and serve with optional toppings.
Notes
• You can use vanilla-flavored Greek yogurt for a sweeter outcome. I like to use yogurt brands sweetened with stevia or monkfruit (without added sugar), such as Oikos Triple Zero or Too Good. • I use almond milk for this recipe, but any type of milk will work. To make it nut-free, simply choose a nut-free milk alternative.• I mix everything directly in the casserole dish to avoid cleaning extra bowls (I’m always trying to cut back on cleaning!). However, if you prefer prepping the mixture in a separate bowl, you can certainly do so. First, add the wet ingredients and mix until smooth and well-combined. Then, add the dry ingredients. Once everything is blended together, transfer the batter into your oiled casserole pan and bake in the oven as directed. • Store leftover oatmeal bake in the fridge for up to 3 days or freeze individual squares for 2 months; reheat in the microwave or thaw on the counter and warm in the oven. • If you’re following a gluten-free diet, be sure to carefully read the packaging for each ingredient, especially the oats (look for brands that are certified gluten-free). While these foods are inherently gluten-free, gluten can sometimes be added during processing for a variety of reasons, including for flavor and consistency.• If you’re looking to make this recipe nut-free, please be sure to use a nut-free milk.
Nutrition information is calculated using a leading industry software. That being said, brands can vary, and there may be slight fluctuations in the numbers.