Casein-Loaded Overnight Oats
A thick, pudding-like jar of oats you build the night before and wake up to already done — 35 grams of protein for around 360 calories, leaning on casein and Greek yogurt so it stays creamy and keeps you full for hours. The breakfast for mornings when you can barely open your eyes.
Plate 01 / Finished
I am not a morning person. Twenty years of early gym sessions and I still wake up like a bear poked out of hibernation — slow, grumpy, useless until I’ve eaten something. For years that meant either skipping breakfast and getting cranky by ten, or eating something rushed and rubbish standing at the counter. Neither did me any favours.
Overnight oats fixed it, and casein made them brilliant. Here’s the simple bit of kitchen science: casein is a slow-digesting milk protein, and when it sits in liquid overnight it thickens everything around it into a proper, spoonable pudding. Stir it into oats with some Greek yogurt and you wake up to a jar that’s thick, creamy, and packed with protein — no blender, no cooking, no thinking required at the hour I think least well.
This is the jar I make before bed on cutting weeks, half-asleep, by feel. Five minutes the night before buys you a breakfast that’s already done when your alarm goes off. It keeps me full clean through to lunch, which matters when calories are tight and a hungry morning is how good plans fall apart. Soft, sweet, sturdy, and kind to your macros — wake up, grab the jar, eat. I’ve got you, even before coffee.
01Who it’s for & when to eat it
Overnight oats are the most flexible breakfast base I know — the oats and protein stay constant, and what you add around them sets the calories. Here’s how I steer it for each job.
The default jar
Oats, casein, Greek yogurt and a handful of berries, kept lean. High protein, properly filling, low enough on calories that it sets you up for a tight day. My go-to cutting breakfast.
Build it up
Bigger oats, a spoon of peanut butter and a sliced banana stirred through. Easy clean calories you can eat half-asleep — perfect for getting food in early when appetite is low. Numbers in the variations below.
Steady fuel
A spoon of nut butter and some seeds for healthy fats, the same slow protein. Releases steadily through the morning and keeps your energy level rather than spiking and crashing.
Timing: this is a slow-digesting breakfast, which makes it brilliant first thing — it keeps you full for hours. The same thick, casein-rich jar also works as a bedtime snack if you like a little slow protein before sleep.
02Ingredients
Makes 1 jar — one generous serving. Doubling for two? Just scale it up and use two jars; there’s no cooking to manage, so it batches beautifully.
Servings 1 · adjust on the live recipe card- Rolled oats40 g · 1.4 oz · ½ cup
- Casein protein powder vanilla25 g · 1 scoop
- Greek yogurt, 0% fat80 g · 2.8 oz
- Milk or unsweetened almond milk120 ml · 4 fl oz
- Mixed berries fresh or frozen60 g · 2 oz
- Chia seeds optional1 tsp
- Vanilla extract½ tsp
- Cinnamona pinch
- Sweetener optional, to tasteto taste
Swaps I actually use: no casein? Whey works, but it makes a looser, soupier jar — add an extra teaspoon of chia to thicken it back up. Dairy-free? Soya yogurt and a plant casein blend hold up best for that pudding texture. No fresh berries? Frozen ones are perfect; they thaw overnight and bleed lovely colour through the oats. A grated apple or a few chopped nuts swap in happily for the topping.
03Step by step
Mix the oats and casein
In your jar, stir together the rolled oats, casein powder, chia seeds if using, and the pinch of cinnamon. Mixing the dry ingredients first stops the casein clumping when the liquid goes in — a small step that saves you a lumpy jar.
Magnus says: dry ingredients first, always. Casein lumps if you pour milk straight onto the powder.
Yogurt, milk, vanilla
Add the Greek yogurt, milk and vanilla extract. Stir well until there’s no dry powder left and you’ve got a smooth, loose mixture — it’ll look too runny right now, and that’s exactly right. It firms up overnight.
Adjust before it sets
Have a quick taste and add a little sweetener if you want it — flavoured casein is often sweet enough on its own, so go easy. This is your one chance to adjust; once it’s set, it’s set.
Magnus says: taste it now. You can’t fix sweetness after a night in the fridge.
Lid on, into the fridge
Put the lid on and leave it in the fridge for at least six hours, or overnight. The oats soften, the chia swells, and the casein thickens the whole thing into a proper creamy pudding while you sleep.
Berries on, spoon in
In the morning, give it a stir, loosen with a splash of milk if you like it looser, and pile the berries on top. Eat it cold straight from the jar — no warming, no fuss, breakfast already made.
04The spec sheet
Real numbers, calculated — not guessed. This makes one generous jar, about 360g of food. Here’s what the whole serving and a flat 100g actually give you.
| Nutrient | Per serving | Per 100g |
|---|---|---|
| Energy | 360 kcal | 100 kcal |
| Protein | 35.0 g | 9.7 g |
| Carbohydrate | 42.0 g | 11.7 g |
| — of which sugars | 14.0 g | 3.9 g |
| Fat | 6.0 g | 1.7 g |
| — of which saturates | 1.5 g | 0.4 g |
| Fibre | 7.0 g | 1.9 g |
| Sodium | ~0.20 g | ~0.06 g |
Low for a breakfast. The yogurt and milk bring water and bulk, so you get a big, filling jar for the calories — and the slow protein keeps you satisfied for hours, which is the real win on a cut.
A lifter’s metric, and strong for a carb-based breakfast. A big share of these calories is protein — rare and valuable first thing in the morning.
- Calcium~350 mg · 35% DV
- Vitamin C~20 mg · 22% DV
- Manganese~1.5 mg · 65% DV
- Phosphorus~350 mg · 50% DV
- Magnesium~70 mg · 17% DV
- Vitamin B12~0.9 µg · 38% DV
Macros are calculated from standard food-composition data and will shift a little with your exact ingredients and brands — protein powders vary a lot, so check your tub. Micronutrient figures are estimates against general adult Daily Values. Numbers are for guidance, not medical advice — see our Nutrition Disclaimer.
05Bulk / Cut / TRT variations
One base, three jobs. The oats and casein stay the same — you adjust the carbs and fat around them. Macros below are for a full serving.
The lean default
Oats, casein, 0% yogurt, almond milk and berries, kept tight. High protein, low fat, properly filling — this is the jar I make through a cut to keep the morning from falling apart.
Build it up
60g oats, a sliced banana and a tablespoon of peanut butter stirred through, full-fat milk. Easy clean calories you can eat half-asleep — ideal when appetite’s low and you need food in early.
Steady & balanced
The default jar with a spoon of almond butter and a scatter of seeds for healthy fats. Slow-releasing protein and steady carbs — level energy through the morning, no spike and crash.
06Meal prep & storage
This is practically built for meal prep — the whole point is making it ahead. I’ll line up three or four jars on a Sunday night and have breakfast sorted for half the week before I’m even out of the kitchen.
Sealed jars keep beautifully for up to four days. The texture actually improves over the first day or two as everything settles into that pudding consistency.
I don’t freeze these — the yogurt splits and the texture goes grainy on thawing. Four days in the fridge is plenty; just batch a few jars at a time.
Keep crunchy toppings like nuts or granola separate and add them just before eating, so they stay crisp instead of going soft in the jar.
If you’re prepping for the week, make a batch of four jars at once — same five minutes of work, four mornings sorted. Hold the berries and any crunchy toppings until the morning so the base stays clean and the textures stay right.
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07Common questions
Why casein instead of whey? +
Two reasons. Casein is a slow-digesting protein, so it keeps you full for longer — exactly what you want from a breakfast on a cut. And it thickens liquid as it sits, which turns runny oats into a proper creamy pudding overnight. Whey does neither as well; it digests fast and stays loose, so the jar comes out soupier.
Can I use whey if that’s what I have? +
You can, and it’ll still taste good — just expect a thinner, more pourable result. To get some of that thickness back, add an extra teaspoon of chia seeds and use a touch less milk. It won’t be quite the same pudding texture, but it’ll do the job and hit the protein.
Do I have to use protein powder at all? +
No — you can lean harder on Greek yogurt and skyr to push the protein up without any powder. You’ll add a little volume and a touch more calories to hit the same protein, but it works fine and tastes great. The powder just makes it easy to get 35g into a small, low-calorie jar.
How do I turn this into a bulk breakfast? +
Add carbs and fat. Use 60g of oats instead of 40, stir in a tablespoon of peanut butter and a sliced banana, and use full-fat milk. That takes the jar from around 360 to roughly 640 calories with 42g protein — easy clean calories you can eat half-asleep. See the Bulk variation above for the numbers.
Can I eat it warm? +
You can — pop it in the microwave for a minute or so and stir. It loses a little of that thick, cold-pudding texture and the protein can go slightly grainy if you overheat it, so go gentle. I prefer it cold straight from the jar, but on a freezing morning, warm is lovely too.
This jar lives inside a full week of meals.
These casein oats are one breakfast in my 7-day cutting plan — seven days of high-protein, low-calorie meals with the macros counted and the grocery list written. You pick the goal; I do the maths.
See the cutting meal plan →08Pairs well with
Magnus Olafsson
I’m Magnus — twenty years under the iron, from a cold gym in Stockholm to the classic-physique stage, and now mostly in my kitchen in a pink apron. I’ve cut for shows, bulked through winters, and I’ve been on TRT since I was thirty-five. I know what it takes to eat for the body you’re chasing, and I know it shouldn’t come with a side of shame.
Everything here is food I actually cook and macros I actually count. I don’t diagnose, I don’t promise, and I never make a number up. I just feed you well and tell you the truth.
Slim Diet Era shares recipes and general nutrition information. It is not medical or dietetic advice, and we do not provide guidance on obtaining or using any controlled substance. See our Medical Disclaimer and Nutrition Disclaimer.