This vegetarian breakfast casserole with Swiss chard and Gruyere is a make-ahead strata that’s perfect for feeding a crowd. Cubes of crusty bread are layered with sautéed vegetables, eggs, milk, and plenty of cheese, soaked overnight, then baked in the morning into a savory breakfast. It reheats beautifully and makes a fantastic brunch centerpiece—or a stellar packed lunch.
Let's get this strata started!
Calling all reluctant morning people! Today I want to share one of my all-time favorite things to make for breakfast, packed lunches, or even those blessed breakfast-for-dinner nights.
If you’ve never made a strata before, think of it as the coziest vegetarian breakfast casserole: layers of crusty bread, sautéed veggies, and plenty of cheese, all soaked overnight in a rich, eggy custard. We've got a considerable archive of healthy vegetarian breakfast recipes here on HNL, but this is for sure one of my faves.
Come morning, all you need to do is pry your eyes open enough to operate the oven and slide your overnight breakfast casserole in to bake while you sip your oat milk matcha latte (or whatever fuels your brain cells).
As it puffs up and turns golden, your kitchen will smell absolutely incredible. About 45 minutes later, you’ll have a gloriously cheesy, veggie-packed Swiss chard and Gruyere breakfast strata ready to slice and serve.
Shall we make some? I’ll show you how!
Let's make this vegetarian breakfast casserole together!
You'll find detailed instructions in the recipe card at the end of this post, but for now, let's walk through it step-by-step.
Step 1: sauté the veggies
Alright, first things first, we're going to heat a bit of olive oil in a large frying pan. Add the onions, and fry until translucent. Then, add the Swiss chard and sauté, stirring frequently, until the greens are wilted but the stems still have a bit of crunch.
Step 2: make the custard mixture
Combine the eggs, milk, mustard, salt, and pepper in a large bowl and whisk until smooth.
Step 3: start layering!
Generously butter a large rectangular casserole dish. Scatter ⅓ of the cubed bread over the bottom. It won't fully cover the bottom (see photo below), but that's ok. Scatter ⅓ of the Swiss chard mixture over the bread.
Scatter ⅓ of the cheeses over top of the swiss chard mixture.
Repeat these steps two more times until you've layered all of the ingredients into your casserole dish.
Step 4: pour + soak
Pour the egg custard over the bread, cheese, and vegetables.
Cover the casserole dish and place it in the fridge. Your strata needs to soak in the fridge for at least four hours, but up to 24 hours.
Step 5: time to bake!
Good morning! It's time to bake this thing! Fire on your oven, and sling the casserole in there.
The strata will bake for 45-55 minutes, and is done when it's puffed, golden, and only slightly jiggly in the middle. When it's finished baking, let it rest for about 10 minutes before serving.
Step 6: serve!
Now you can serve warm scoops of bready, cheesy, comforting goodness onto waiting plates and dig in!
Vegetarian Breakfast Casserole with Swiss Chard and Gruyere
Ingredients
- 1 Tablespoon extra virgin olive oil
- 1 medium yellow onion diced
- 1 large bunch Swiss chard washed and roughly chopped
- 8 cups cubed whole grain bread in one-inch cubes I used a sourdough rye
- 2 cups coarsely grated gruyere
- 1 cup finely grated Parmesan cheese
- 9 large eggs
- 2 Tablespoons smooth dijon mustard
- 2¾ cups milk
- 1 teaspoon salt
- freshly ground black pepper
Instructions
- Heat olive oil in a large skillet over medium-high heat.1 Tablespoon extra virgin olive oil
- Add the onion, and sauté for about 3 minutes, until translucent.1 medium yellow onion
- Add the Swiss chard, and sauté until wilted and the stems are slightly browned. Season with salt and pepper and remove from the heat.1 large bunch Swiss chard
- Generously butter a 9x13 casserole dish.
- Layer one-third of the bread cubes over the bottom of the dish. It won't fully cover the bottom, but this is ok.8 cups cubed whole grain bread in one-inch cubes
- Layer one-third of the sautéd chard over top of the bread, followed by one-third of the gruyere, and one-third of the Parmesan.2 cups coarsely grated gruyere, 1 cup finely grated Parmesan cheese
- Repeat these layers two more times.
- Whisk eggs together with Dijon mustard, then whisk in the milk, salt, and pepper.9 large eggs, 2 Tablespoons smooth dijon mustard, 2¾ cups milk, 1 teaspoon salt, freshly ground black pepper
- Pour the custard over top of the strata layers. Cover with plastic wrap, and set in the fridge overnight or for at least four hours, but up to one day.
- When you're ready to bake, preheat the oven to 350°F /180°C.
- Bake the strata for 45-55 minutes, until it is puffed and golden on top, and no longer so jiggly in the middle (a little jiggle is ok as it will continue to cook as it cools).
- Remove from the oven and let stand for 10 minutes before serving.
Notes
- If you don't have Swiss chard you can substitute another sturdy leafy green, such as kale, collard greens, or mustard greens.
- Any sharp cheese can be used in place of the gruyere, but it really is delicious.
- I don't have a lot of fridge space, so I often just soak on the counter for an hour before baking. This is totally fine.
- Cooled strata can be sliced into squares, wrapped in foil, and frozen for quick and easy meals. They make for a great packed lunch.
- Nutrition values are an estimate only.
Ashley says
Hi Katie! Anyone make it with gluten free bread?
Katie Trant says
Hi Ashley! I haven't tested this with gluten-free bread, but I don't see why it wouldn't work out. If you try it, please let us know in the comments!
Emily says
Made this for dinner this week and it’s doing double duty for lunchtime leftovers. My 9 month old baby gobbled it up too. Winner!
Katie Trant says
My little guy also loves this strata!
Julia says
Hi Katie, When this dish gets wrapped in foil and frozen to defrost can it travel for example to work in the foil, defrosting slowly, then put in fridge until lunch when it then I assume gets put in a low temperature oven to heat up? Thanks for the recipe!
Katie Trant says
Hi Julia! When I take it to work for lunch I just throw it in my bag frozen, still wrapped in the foil. I keep it by my desk at work and by lunch time it's usually still slightly frozen, so then I remove the foil and heat for a few minutes in the microwave. You could also defrost it overnight in your fridge, keep it in the fridge at work, and then reheat. Reheating in a low-temp oven would also work, but at my office all there is are microwaves, so that's what I use.
Cammy says
Wow, That was really good!
Katie Trant says
Yeah! It's not going to win any beauty contests, but it sure is tasty!
Anne T. says
Katie, thank you for posting this recipe. I made it tonight, and the taste and texture are amazing. I used rye bread, too, and that definitely enhances the other flavors. It literally melts in your mouth, and I love the fact that I now have dinner for two for four more nights!
So glad you're back, and congratulations on Baby Muffin Myth 🙂
Katie Trant says
Thanks Anne! I'm so glad you made this strata. It's one of my favourites for quick and easy meals, and your leftovers will freeze like a charm! Enjoy 🙂
Joyce says
Sounds delicious, and have loads of rainbow chard in garden. But I'm gluten intolerant. In a vaguely similar eggs and cheese dish I've replaces bread with rice flakes. Do you think that would work here?
Katie Trant says
I honestly have no idea as I've never tried such a thing, but if you do try it please let us know how it works out!