vernight oats are one of the easiest ways to guarantee a high-calorie start to the day, because you build the whole thing the night before, leave it in the fridge, and it is ready to eat cold in the morning with no cooking. That makes them especially useful for gaining weight, when the hardest part is often eating enough consistently: a jar prepared the evening before removes the morning effort entirely, and a well-built one delivers 600 to 900 calories in a soft, spoonable serving.

This guide gives you a high-calorie overnight oats recipe, explains the ingredients that make it calorie-dense, and covers how to adapt it for a low appetite, for extra protein, and for vegan or gluten-free diets. It is written for people who need to eat more, not less, and sits alongside our wider how to gain weight guide. If you would prefer a crunchy option, see our high-calorie granola guide instead.

I am James Frost, founder of Flaming Phoenix. I built Phoenix Bars, a soft oat-based bar, after around 150 conversations with endurance athletes and people who struggle to eat enough. A recurring theme in those conversations was that the calories people miss most are the ones that need effort at a busy or low-appetite moment, which is exactly the problem a make-ahead breakfast solves.

Why overnight oats work so well for gaining weight

Three things make overnight oats particularly effective when the goal is more calories. They are make-ahead, so the meal is done before the morning rush or before appetite is at its lowest, which removes the single biggest reason people skip calories. They are soft and spoonable, having absorbed liquid overnight, which makes them far easier to eat than a big dry bowl when you are not especially hungry, and puts them among the more useful soft high-calorie foods. And they are endlessly adaptable, so you can load calorie-dense ingredients into the same simple base without changing the method.

The key point, and the thing the weight-loss versions get backwards, is that the base is not what makes overnight oats high or low calorie. It is what you add. Oats in water with a splash of skimmed milk is a light breakfast. The same oats in full-fat milk with yoghurt, nut butter, seeds and banana is a substantial, calorie-dense meal. The recipe below is built the second way.

A high-calorie overnight oats recipe

This makes one generous serving of roughly 700 calories, and it takes about three minutes to assemble the night before. Scale the add-ins up or down to hit your own target.

In a jar or container, combine 60g rolled oats (rolled oats work best, as steel-cut stay too firm and instant can turn mushy), 200ml full-fat milk or a full-fat plant milk such as coconut or soy, and 100g full-fat Greek yoghurt, which is the main protein source. Stir in a heaped tablespoon of peanut, almond or cashew butter, a tablespoon of chia or ground flax seeds, and a teaspoon of honey or maple syrup with a little vanilla or cinnamon for flavour. Seal and refrigerate for at least five hours, ideally overnight. In the morning, top with a sliced banana, a handful of chopped nuts, and a drizzle more nut butter or honey if you want to push the calories higher.

To take a single jar towards 900 calories or more, add a second tablespoon of nut butter, a spoon of full-fat coconut milk (the tinned kind, not the carton drink), or a handful of dried fruit and dark chocolate. Each of those adds 100 to 200 calories without meaningfully changing how much there is to eat.

The ingredients that add the most calories

If you would rather build your own version, these are the levers, roughly in order of impact. The liquid you choose sets the baseline, so full-fat milk, tinned coconut milk or half-and-half beat skimmed milk or a light plant milk by a wide margin. Nut butter is the most efficient single addition, adding around 100 calories plus protein and fat per heaped tablespoon. Full-fat Greek yoghurt adds calories and, importantly, the protein oats lack. Seeds, especially chia, flax and hemp, add calories, nutrients and a thicker texture. Banana, dried fruit, honey or maple syrup add quick carbohydrate calories and natural sweetness. Chopped nuts, chocolate or shredded coconut add richness and crunch on top. Building from a rich liquid and adding two or three of these is all it takes to reach 700 calories or beyond, and the same approach powers a good high-calorie breakfast more broadly.