Zucchini Casserole

This zucchini casserole layers ribbons of zucchini over a savoury filling of mushrooms, rice, garlic and fresh herbs, then bakes until set. It makes 8 budget-friendly servings, holds together neatly once cooled, and is exactly the kind of dish you cook once when a busy week is coming and eat happily for days.

I usually make a casserole when I have a very busy week ahead and don’t have time to cook something different each day. This one fed two of us for three days, and we kept it interesting by serving it with different sides each time so we wouldn’t get bored of the taste: pickled veggies, simple salads, a white sauce one night and a red one the next.

If I’m being completely open about it, the filling resembles my mushroom pilaf a lot. That’s the part I love most here. The mushrooms and rice do the heavy lifting on flavour, and the zucchini wraps everything in a light, almost lasagne-like structure without any pasta at all.

When to make this

This is a make-once, eat-all-week dish. An average casserole takes about an hour to put together but feeds a crowd, so it earns its place when you are cooking for a family, batch-cooking for the days ahead, or simply want one tray in the fridge that you can reheat and dress up differently each time. It travels well to a potluck too, since it slices cleanly once it has cooled.

Key ingredients

Zucchini is the star and the structure here. You’ll peel each one into long ribbons with a regular vegetable peeler, which is why you want firm, fresh zucchini rather than soft, oversized ones that turn watery. Four medium zucchinis give you enough ribbons to cover the bottom and top of the tray.

Button mushrooms bring the savoury, meaty depth that makes this casserole satisfying. Half a kilo sounds like a lot, but mushrooms shed most of their water as they cook and shrink dramatically, concentrating their flavour into the filling.

Rice soaks up the mushroom liquid and binds the filling. One cup is enough to give body without making the dish stodgy. It finishes cooking in the oven, so you are aiming for slightly underdone on the stovetop, not fully soft.

Psyllium husks are the binder that holds the filling together once baked. Three tablespoons gel with the residual moisture and keep your slices from crumbling. If you don’t keep psyllium on hand, ground flax seeds work the same way, or two beaten eggs if you are happy to make it vegetarian.

Fresh parsley and dill are not a garnish afterthought here. Stirred in at the end, off the heat, they keep their colour and brightness and lift the earthy mushrooms. The thyme, oregano and ground coriander seeds build the warm base note underneath.

Tips for getting it right

• Cook the mushrooms covered. Putting a lid on the pan after the mushrooms go in traps the steam and helps them release their water, so they soften and concentrate rather than dry out.
• Leave the rice slightly underdone. When you taste the filling, the rice should be just shy of fully cooked. It absorbs more moisture and finishes in the oven, so fully soft rice on the stovetop will end up mushy.
• Don’t waste the zucchini cores. Once you peel the ribbons, the middle of each zucchini won’t turn into more ribbons. Cube that part and stir it into the mushroom and rice filling so nothing goes to waste.
• Season the filling properly. Taste before you assemble and check it is salty enough. The zucchini ribbons on top are unseasoned until the final spray, so the filling needs to carry the dish.
• Let it cool before slicing. The single most common mistake is cutting into it straight out of the oven. Give it a few minutes to set and you’ll get clean slices instead of a crumbly mess.

Variations and swaps

The binder is the most flexible part. Psyllium husks, ground flax seeds, or two beaten eggs all hold the filling together, so use whichever you have. If you want a richer, cheesy version of a zucchini casserole instead, I have an older recipe with cheese over on my vegetarian zucchini and cheese bake. And if you love zucchini as much as I do, my zucchini and mushroom moussaka uses the same vegetables in a completely different way.

Storage and make-ahead

This casserole is built for leftovers. Once cooled, it keeps in the fridge for up to three or four days in an airtight container, and the slices actually firm up and hold together better on day two. Reheat portions in the oven or a covered pan, and change up the sides each time to keep it interesting, the way I do. For more batch-friendly ideas, browse my full collection of vegan casserole recipes.

Zucchini Casserole

This hearty vegan zucchini casserole layers tender zucchini ribbons over a savory mushroom-and-rice filling. It’s made with budget-friendly ingredients and bakes up comforting enough for the whole family.

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Prep Time 10 minutes minutes

Cook Time 1 hour hour

Total Time 1 hour hour 10 minutes minutes

Choose Serving Size 9

Ingredients 

• 4 zucchinis
• 500 g button mushrooms
• 1 cup rice
• 1 onion diced
• 3 cloves garlic mashed
• 3 Tbsp psyllium husks or replace with ground flax seeds
• 1 tsp thyme
• 1 tsp oregano
• 1 tsp ground coriander seeds
• ½ cup parsley chopped
• ⅓ cup dill chopped
• 2 Tbsp oil
• sea salt and pepper to taste

Instructions

• Chop the button mushrooms and dice the onion.
• Heat the oil in a large pan. Add the onion and garlic and saute for 2 minutes.
• Add the mushrooms and all the spices. Cover with a lid and let them cook for 10 minutes.
• Add the rice and 2 cups of water. Cover with a lid and cook for 10 more minutes.
• Check whether the rice has absorbed the liquid. Cook until most of the liquid is absorbed (max. 10 more minutes).
• Taste and check if it’s salty enough. Don’t worry if the rice is slightly undercooked – that’s ok, it will finish cooking in the oven. Add the herbs and psyllium husks (or the replacement mentioned above) and mix.
• Using a peeler, start peeling the zucchinis into ribbons.
• You’ll notice the middle part of each zucchini cannot be turned into ribbons. Don’t throw it away – cut it into small cubes and mix it into the mushroom-rice filling.
• Grease an oven tray, like the one in the photos, and place half of the zucchini ribbons on it.
• Add the mushroom and rice filling and spread it evenly.
• Top with the rest of the zucchini ribbons.
• Season with salt and pepper and spray with a little oil.
• Bake in the oven at 375F (190C) for 20 minutes.

Notes

Tip: If you want to slice it neatly, without any mess or crumbling, let it cool a little before cutting. Store leftovers in an airtight container in the fridge for up to 3 days.

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