Baked Oatmeal Recipe for a 9x13 Pan: Easy & Crowd-Friendly

Baked oatmeal is a comforting, hearty breakfast dish that combines the wholesome goodness of oats with the convenience of a one-pan bake. Using a 9×13 inch pan allows you to prepare a generous batch perfect for families or meal prep, delivering a warm, chewy texture with crispy edges that everyone loves.

Ingredients

3 cups old-fashioned rolled oats
1/2 cup brown sugar, packed
1 teaspoon baking powder
1 1/2 teaspoons ground cinnamon
1/2 teaspoon salt
2 cups milk (whole, 2%, or plant-based)
2 large eggs
1/4 cup unsalted butter, melted (or coconut oil)
2 teaspoons vanilla extract
1 cup fresh or frozen berries (blueberries, raspberries, or mixed)
1/2 cup chopped nuts (walnuts, pecans, optional)
Optional toppings: maple syrup, yogurt, sliced bananas

Instructions

Preheat your oven to 350°F (175°C). Lightly grease a 9×13 inch baking dish with butter or non-stick spray.
In a large bowl, combine the rolled oats, brown sugar, baking powder, cinnamon, and salt. Stir well to evenly distribute the dry ingredients.
In a separate medium bowl, whisk together the milk, eggs, melted butter, and vanilla extract until fully combined.
Pour the wet mixture into the dry ingredients. Stir until the oats are fully coated and the mixture is uniform.
Gently fold in the berries and nuts, reserving a small handful of berries for topping if desired.
Transfer the mixture to the prepared 9×13 pan, spreading it out evenly. Sprinkle the reserved berries on top for a decorative finish.
Bake uncovered for 35-40 minutes, or until the top is golden brown and the baked oatmeal is set in the center. A toothpick inserted near the middle should come out mostly clean with a few moist crumbs.
Remove from oven and let cool for 5-10 minutes before slicing into squares.
Serve warm with optional toppings like maple syrup, yogurt, or fresh fruit.

Tips

Milk Substitutions: Use any dairy or non-dairy milk such as almond, oat, or soy milk. For creamier results, whole milk or a mix of milk and cream works well.
Sweetener Variations: Swap brown sugar for honey, maple syrup, or coconut sugar. Reduce liquid slightly if using a liquid sweetener to maintain texture.
Adding Protein: Stir in a scoop of protein powder or Greek yogurt into the wet ingredients for a more filling breakfast.
Storage: Cool completely before covering and refrigerating. Baked oatmeal keeps well for up to 5 days in the fridge and freezes beautifully for up to 3 months.

Serving Suggestions

Baked oatmeal is delicious on its own but can be elevated with a variety of toppings and sides. Drizzle with warm maple syrup or a dollop of Greek yogurt for creaminess and tang. Fresh fruit like sliced bananas or strawberries adds brightness and freshness. For a savory twist, try sprinkling with a pinch of flaky sea salt and serving alongside scrambled eggs or avocado slices.

Variations

This baked oatmeal recipe is highly adaptable. Try swapping berries for diced apples and adding 1 teaspoon of ground nutmeg for a fall-inspired flavor. For a tropical version, use chopped mango and shredded coconut with a splash of orange juice in place of vanilla. Chocolate lovers can stir in 1/2 cup mini chocolate chips or cocoa powder for a rich treat. To make it vegan, replace eggs with flax eggs (1 tablespoon ground flaxseed + 3 tablespoons water per egg) and use plant-based milk and oil.

Storage and Reheating

After baking, allow the oatmeal to cool completely before storing. Wrap tightly with plastic wrap or transfer to an airtight container. It will keep in the refrigerator for up to 5 days. To freeze, cut into individual portions, wrap each piece in plastic wrap, then place in a freezer-safe bag or container for up to 3 months.

To reheat, microwave a portion for 45-60 seconds until warmed through, or heat in a preheated 350°F (175°C) oven for 10-15 minutes. If reheating from frozen, thaw overnight in the fridge for best texture before warming.

Frequently Asked Questions

Can I use quick oats instead of rolled oats?
Quick oats absorb liquid differently and can result in a mushier texture. Rolled oats are preferred for baked oatmeal because they hold their shape and provide a pleasant chewiness. If you must use quick oats, reduce the liquid slightly and check the baking time as it may be shorter.

Is baked oatmeal gluten-free?
Oats themselves are naturally gluten-free, but cross-contamination can occur during processing. To ensure your baked oatmeal is gluten-free, use certified gluten-free oats. Also, double-check any added ingredients like baking powder or mix-ins for gluten content.

Can I prepare this recipe the night before?
Yes! You can assemble the mixture in the baking dish the night before, cover, and refrigerate. In the morning, bake it fresh. You may need to add a few extra minutes to the baking time if baking straight from the fridge.

How do I make baked oatmeal less dense?
To lighten the texture, avoid packing the oats tightly in the pan and ensure you don’t overmix. Adding a bit more baking powder (up to 1 1/2 teaspoons) or incorporating whipped egg whites folded in gently can also help create a fluffier result.

Can I add other fruits or mix-ins?
Absolutely! Baked oatmeal is very flexible. Chopped apples, pears, dried cranberries, raisins, or even shredded zucchini work well. Just be mindful of moisture content; for juicy fruits, reduce added liquid slightly to avoid sogginess.

Is this recipe suitable for meal prep or freezing?
Yes, baked oatmeal is an excellent make-ahead breakfast. It freezes well in individual portions and reheats quickly. This makes it ideal for busy mornings or feeding a crowd with minimal effort.

With this easy baked oatmeal recipe, you can enjoy a nutritious, comforting breakfast that’s perfect for weekdays or weekends alike. Its versatility and simple preparation make it a go-to dish that suits many tastes and dietary preferences.

Baked Oatmeal Recipe for a 9×13 Pan: Easy & Crowd-Friendly