There’s comfort in a warm bowl of oats that practically makes itself while you sleep. This version uses steel cut oats, mashed bananas and a slow cooker to produce creamy, hearty porridge with a gentle chew—think banana bread in oatmeal form. It’s forgiving, slow, and excellent for busy mornings.

I test and retest breakfasts that need to work every day of the week. This recipe is intentionally straightforward: measured ingredients, a single vessel, and predictable timing. Little prep the night before, and you wake up to breakfast ready to dress up any way you like.

Below you’ll find a clear ingredient rundown, step‑by‑step instructions taken straight from the recipe source, tips for substitutions and equipment, and ways to store or customize the oats. Follow the slow cooker directions exactly for the most consistent outcome.

Ingredient Rundown

Each ingredient below is listed as given in the recipe source with a short note about its role or a practical tip for success.

1.5 cups steel cut oats — do not substitute quick cooking, instant, or rolled oats; gluten free if needed.
4 cups water — provides the main cooking liquid and keeps the oats tender without being too rich.
2 cups milk — any kind you like (I used skim); adds creaminess and a touch of sweetness.
2 large mashed ripe bananas — plus additional banana slices for serving; mashed bananas sweeten and bind, giving banana‑bread flavor.
3 tablespoons ground flaxseed meal* — boosts fiber and helps thicken the oats slightly while adding a mild nutty note.
2 teaspoons pure vanilla extract — lifts and rounds the banana and cinnamon flavors.
1 ½ teaspoons ground cinnamon — warm spice that pairs with banana and nutmeg.
½ teaspoon freshly grated nutmeg — it’s an amazing flavor upgrade to grate your own nutmeg.
½ teaspoon kosher salt — balances sweetness and enhances the overall flavor.
For serving: chopped toasted walnuts — add crunch and toasty flavor.
For serving: raisins, chocolate chips, maple syrup, peanut butter, or any other mix-ins you enjoy with banana bread — choose one or several to finish each bowl.

From Start to Finish: Overnight Slow Cooker Steel Cut Oats

Place 1.5 cups steel cut oats (do not substitute quick, instant, or rolled oats), 4 cups water, 2 cups milk, 2 large mashed ripe bananas, 3 tablespoons ground flaxseed meal, 2 teaspoons pure vanilla extract, 1 ½ teaspoons ground cinnamon, ½ teaspoon freshly grated nutmeg, and ½ teaspoon kosher salt into the bottom of a 4- to 6-quart slow cooker.
Stir the mixture until ingredients are evenly combined and the mashed bananas are distributed throughout.
Cover the slow cooker.
Cook on LOW for 7–8 hours (overnight) or on HIGH for 4 hours, until the oats are soft but still have a bit of chew.
Turn off the slow cooker, remove the lid, and stir the oats thoroughly to combine evenly.
Serve warm with chopped toasted walnuts, additional banana slices, raisins, chocolate chips, maple syrup, peanut butter, or other mix-ins listed in the ingredient section as desired.

Why This Recipe Is Reliable

The recipe locks in reliability by using clear ratios and a long, gentle cooking time. Steel cut oats need extended liquid exposure to soften while retaining texture; the 1.5 cups oats to 6 cups liquid (water + milk) ratio gives a creamy result without going soupy. Mashed bananas contribute sweetness and body, reducing the need for added sugar and helping the porridge set into a pleasant consistency.

Slow cookers vary, but the time window—7–8 hours on LOW or 4 hours on HIGH—creates a safe margin. The oats finish tender with a slight chew rather than turning to mush. Stirring immediately after cooking ensures the mashed banana distributes evenly and the flaxseed meal is fully incorporated, avoiding clumps.

Because the ingredients are pantry‑stable (oats, water, milk, spices) and the method keeps hands‑off most of the time, this is a repeatable weekday staple. Little can go wrong if you don’t substitute the oats for a faster type—those will overcook and lose the intended texture.

Substitutions by Category

Oats — Do not substitute steel cut oats with quick, instant, or rolled oats; they cook differently and will overcook in a slow cooker.
Liquid — Replace part or all of the milk with any plant milk you prefer for flavor or dietary needs (as noted in the ingredient list: any kind you like).
Bananas — If you need less banana flavor, reduce to one mashed banana, but expect less natural sweetness and body; you can add sweeteners at serving time.
Fiber / Thickener — The ground flaxseed meal thickens and adds fiber; if omitted, the oats will be slightly looser but still fine—stir well after cooking to check texture.
Mix-ins & toppings — Use the listed serving items: chopped toasted walnuts, raisins, chocolate chips, maple syrup, peanut butter, additional banana slices. Combine them to taste rather than following strict measurements.

Setup & Equipment

Use a 4‑ to 6‑quart slow cooker so the mixture has room to expand and to prevent spillover. A ceramic or stoneware insert with a tight‑fitting lid works well. Measure liquid and oats with proper measuring cups; a small bowl and fork for mashing bananas speeds up prep. Have a wooden spoon or heat‑safe silicone spatula for the final stir.

Extras that help but aren’t required: a microplane or fine grater for fresh nutmeg, a small skillet or oven for toasting walnuts ahead of time, and airtight containers for leftovers. If your cooker runs hot, test the high setting the first time you try this recipe and check texture at 3.5 hours to avoid overcooking.

Don’t Do This

Do not substitute quick, instant, or rolled oats for the steel cut oats—texture and cook time are not interchangeable.
Don’t lift the slow cooker lid to check frequently during the long cook; it steals heat and increases overall time needed.
Don’t skip stirring after cooking—mashed banana and flaxseed can clump if not combined thoroughly.
Avoid overfilling a small slow cooker. Use a 4–6 quart cooker to prevent boil‑over and ensure even cooking.
Don’t assume every slow cooker yields the same result; test the first time you run this recipe on your specific unit and note whether you prefer the LOW or HIGH timeline for future runs.

Variations by Season

This base recipe is a canvas that works year‑round. Use the ingredient list items to make seasonally appropriate bowls without changing the core ingredients.

Autumn — Emphasize cinnamon and freshly grated nutmeg; top with chopped toasted walnuts and a drizzle of maple syrup for a cozy, warming bowl.
Winter — Add chocolate chips and a spoonful of peanut butter at serving for a richer, indulgent finish that pairs well with the banana base.
Spring — Keep it light: banana slices and a scattering of raisins with a small drizzle of maple syrup make a fresh, simple presentation.
Everyday — Rotate walnuts, raisins, chocolate chips, and peanut butter as your pantry dictates—each gives a distinct texture and flavor profile while staying within the recipe’s serving suggestions.

Flavor Logic

The ingredients are chosen to balance sweetness, spice and texture. Mashed bananas supply natural sugar and body, meaning you don’t need refined sugar. Vanilla rounds the fruit and spice notes. Cinnamon and freshly grated nutmeg are complementary warm spices; cinnamon gives sweeter, aromatic top notes while nutmeg provides a slightly savory warmth that deepens the banana bread vibe.

Ground flaxseed meal acts as a fiber booster and gentle binder, helping the oats hold together without making them gummy. Milk contributes creaminess; water keeps the texture light and prevents the mixture from becoming too rich. Salt is small but essential—without it the flavors lack contrast.

Make-Ahead & Storage

These oats store well. Cool the pot slightly, then transfer leftovers to airtight containers. Refrigerate for up to 4–5 days. Reheat portions in the microwave with a splash of milk or water to loosen the texture, or warm gently on the stovetop, stirring until hot. Add any mix-ins after reheating to retain texture (chopped toasted walnuts stay crisp if added at serving).

Freezing is possible but changes the texture: portion the cooled oats into freezer‑safe containers and freeze up to 2 months. Thaw overnight in the fridge and reheat with a bit of liquid. Note that flaxseed and mashed banana can alter texture after freezing and thawing; stirring well after reheating restores a smooth consistency.

Serve & Enjoy

Serve the oats warm, straight from the slow cooker. Top with chopped toasted walnuts for crunch, extra banana slices for freshness, a handful of raisins or chocolate chips for sweetness, and a drizzle of maple syrup or a spoonful of peanut butter if you like. Create individual bowls at the table so everyone can pick their favorite combination.

This breakfast is uncompromisingly simple to make and versatile to eat. It stores well, feeds a crowd, and improves with small habit tweaks—toast the walnuts ahead, grate nutmeg fresh, or pre‑mash bananas and freeze them for faster prep. Most importantly: follow the oats and liquid ratio and the slow cooker timing for the best, most reliable results.

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Overnight Slow Cooker Steel Cut Oats

Steel cut oats cooked overnight in a slow cooker with mashed bananas, flaxseed, milk, and warm spices. Cook on LOW for 7–8 hours or on HIGH for 4 hours and serve with your favorite mix-ins.

Prep Time10

Cook Time8

Total Time8 10

Course: Breakfast

Servings: 6 servings

Ingredients

1.5 cupssteel cut oatsdo not substitute quick cooking instant, or rolled oats, gluten freeif needed
4 cupswater
2 cupsmilkany kind you like I used skim
2 large mashed ripe bananasplus additional banana slices for serving
3 tablespoonsground flaxseed meal*
2 teaspoonspure vanilla extract
1 1/2 teaspoonsground cinnamon
1/2 teaspoonfreshly grated nutmegit’s an amazing flavor upgrade to grate your ownnutmeg. I usethis zesterto do it.
1/2 teaspoonkosher salt
For serving: chopped toasted walnutsraisins chocolate chips, maple syrup, peanut butter, or any other mix-ins you enjoy with banana bread

Instructions

Place 1.5 cups steel cut oats (do not substitute quick, instant, or rolled oats), 4 cups water, 2 cups milk, 2 large mashed ripe bananas, 3 tablespoons ground flaxseed meal, 2 teaspoons pure vanilla extract, 1 ½ teaspoons ground cinnamon, ½ teaspoon freshly grated nutmeg, and ½ teaspoon kosher salt into the bottom of a 4- to 6-quart slow cooker.
Stir the mixture until ingredients are evenly combined and the mashed bananas are distributed throughout.
Cover the slow cooker.
Cook on LOW for 7–8 hours (overnight) or on HIGH for 4 hours, until the oats are soft but still have a bit of chew.
Turn off the slow cooker, remove the lid, and stir the oats thoroughly to combine evenly.
Serve warm with chopped toasted walnuts, additional banana slices, raisins, chocolate chips, maple syrup, peanut butter, or other mix-ins listed in the ingredient section as desired.

Equipment

4- to 6-quart slow cooker

Notes

Notes
Overnight steel cut oats can be refrigerated for up to 1 week or frozen for up to 2 months. To reheat, top desired amount with a few tablespoons of water or milk, then warm in the microwave or in a small saucepan until hot. If the oatmeal is frozen, let thaw overnight in the refrigerator first.
*The ground flaxseed meal I added for a nutritional boost. If you don’t have it or do not wish to add it, simply omit it. You can also substitute
chia seeds
or
hulled hemp seeds
.