Quick Recipe Version (TL;DR)
Quick Ingredients
- Nonstick spray or butter (for the pan)
- 3 cups (270 g) old-fashioned rolled oats
- 2 teaspoons baking powder
- 2 teaspoons ground cinnamon
- 1/2 teaspoon fine salt
- 1/4 teaspoon ground nutmeg (optional)
- 2 medium apples, peeled or unpeeled, diced small (about 3 cups / 360 g)
- 1/2 cup (60 g) chopped walnuts
- 2 1/2 cups (600 ml) milk (dairy or unsweetened non-dairy)
- 2 large eggs (or 2 flax eggs; see Full Ingredients)
- 1/4 cup (60 ml) pure maple syrup
- 2 tablespoons melted butter or coconut oil (optional, but tasty)
- 2 teaspoons vanilla extract
- To serve: Greek yogurt and fresh berries
Do This
- 1) Heat oven to 375°F (190°C). Grease a 9×13-inch baking dish.
- 2) Mix dry: oats, baking powder, cinnamon, salt, and nutmeg.
- 3) Whisk wet: milk, eggs (or flax eggs), maple syrup, melted butter (optional), and vanilla.
- 4) Stir wet into dry. Fold in diced apples and walnuts.
- 5) Pour into pan and bake 35–40 minutes, until set and lightly golden.
- 6) Cool 20 minutes, then cut into 12 squares for meal prep.
- 7) Serve topped with Greek yogurt and berries; refrigerate extras.
Why You’ll Love This Recipe
- Meal-prep friendly: Bakes in one pan, slices neatly, and reheats beautifully.
- Cozy flavors: Warm cinnamon, vanilla, apples, and toasted walnuts in every bite.
- Flexible: Works with eggs or flax eggs, dairy or non-dairy milk, and lots of mix-in options.
- Balanced breakfast: Whole grains, fruit, and protein-rich toppings keep it satisfying.
Grocery List
- Produce: 2 medium apples, fresh berries (about 2 cups)
- Dairy: Milk (2 1/2 cups), Greek yogurt (about 1 1/2 cups), 2 large eggs (if using)
- Pantry: Old-fashioned rolled oats, baking powder, ground cinnamon, salt, vanilla extract, pure maple syrup, walnuts, nutmeg (optional), ground flaxseed (if making flax eggs), butter or coconut oil (optional)
Full Ingredients
Baked Oatmeal Base
- Nonstick spray or softened butter, for greasing the pan
- 3 cups (270 g) old-fashioned rolled oats (not quick oats)
- 2 teaspoons baking powder
- 2 teaspoons ground cinnamon
- 1/2 teaspoon fine salt
- 1/4 teaspoon ground nutmeg (optional, but great with apples)
Mix-Ins
- 2 medium apples, diced small (about 3 cups / 360 g)
- 1/2 cup (60 g) chopped walnuts
Wet Ingredients
- 2 1/2 cups (600 ml) milk (2% milk, whole milk, or unsweetened non-dairy milk)
-
2 large eggs
or 2 flax eggs (for egg-free): mix 2 tablespoons ground flaxseed with 5 tablespoons water, let thicken 5 minutes - 1/4 cup (60 ml) pure maple syrup
- 2 tablespoons melted butter or coconut oil (optional, for a richer texture)
- 2 teaspoons vanilla extract
For Serving (Optional but Recommended)
- 1 1/2 cups plain Greek yogurt (about 2 tablespoons per square)
- 2 cups fresh berries (strawberries, blueberries, raspberries, or a mix; about 1/4 cup per square)
- Extra cinnamon and/or an extra drizzle of maple syrup (optional)
Step-by-Step Instructions
Step 1: Preheat the oven and prepare your pan
Preheat your oven to 375°F (190°C). Lightly grease a 9×13-inch baking dish with nonstick spray or butter.
If you want very clean, lift-out slices, you can line the dish with parchment paper (leave a little overhang on the long sides), then grease the parchment lightly.
Step 2: If using flax eggs, mix them now
If you’re making the egg-free version, stir together 2 tablespoons ground flaxseed and 5 tablespoons water in a small bowl. Let it sit for 5 minutes to thicken to a gel-like consistency.
Step 3: Mix the dry ingredients
In a large bowl, combine the rolled oats, baking powder, cinnamon, salt, and nutmeg (if using). Stir well so the leavening and spices are evenly distributed.
Step 4: Whisk the wet ingredients
In a separate bowl (or a large measuring pitcher), whisk together the milk, eggs (or the prepared flax eggs), maple syrup, melted butter/coconut oil (if using), and vanilla until smooth.
Step 5: Combine, then fold in apples and walnuts
Pour the wet mixture into the bowl with the dry ingredients. Stir until everything is evenly moistened; the mixture will look loose, and that’s exactly right.
Fold in the diced apples and chopped walnuts. Make sure the apples are evenly spread throughout so every square gets fruit.
Step 6: Bake until set and lightly golden
Pour the mixture into your prepared baking dish and smooth the top with a spatula.
Bake for 35–40 minutes, or until the center is set (no longer looks wet) and the edges are lightly golden. If you gently press the center, it should feel springy and hold together.
Step 7: Cool, slice, and serve with toppings
Let the baked oatmeal cool in the pan for 20 minutes. This cooling time helps it firm up so you can cut clean squares.
Slice into 12 squares. Serve warm or at room temperature, topped with Greek yogurt and fresh berries. For extra coziness, add a light dusting of cinnamon or a small drizzle of maple syrup.
Pro Tips
- Dice the apples small: Aim for about 1/4-inch pieces so they soften evenly and distribute well through the squares.
- Don’t overbake: Pull it when the center is set but still tender. Overbaking can make baked oatmeal dry.
- Cool before slicing: A full 20 minutes makes a big difference for tidy, meal-prep-friendly squares.
- Toast the walnuts (optional): For deeper flavor, toast chopped walnuts in a dry skillet over medium heat for 3–5 minutes, then cool before adding.
- Prefer softer, more “spoonable” baked oatmeal? Bake in an 8×8-inch dish and scoop portions instead of slicing squares, or add an extra 1/4 cup milk.
Variations
- Raisin-apple cinnamon: Swap half the walnuts for 1/3 cup raisins (or add both).
- Apple pie spice: Replace the cinnamon and nutmeg with 1 tablespoon apple pie spice.
- Higher-protein version: Use high-protein milk (like ultra-filtered dairy milk) and serve with an extra-big dollop of Greek yogurt.
Storage & Make-Ahead
Let squares cool completely, then store in an airtight container in the refrigerator for up to 5 days.
To reheat: Microwave 1 square for 25–40 seconds (depending on your microwave), or warm in a 350°F oven for 8–10 minutes. Add yogurt and berries after reheating.
To freeze: Wrap individual squares tightly and freeze up to 3 months. Thaw overnight in the fridge or microwave from frozen in short bursts until warmed through.
Nutrition (per serving)
Approximate per square (1/12 of the pan, without toppings): 200 calories, 6 g protein, 30 g carbs, 8 g fat, 5 g fiber, 10 g sugars, 180 mg sodium.
With toppings (plus 2 tablespoons Greek yogurt and 1/4 cup berries): about 250 calories, 9 g protein, 34 g carbs, 9 g fat.
