Cheesy Zucchini Gratin
Layers of tender zucchini, soft onion and Gruyère baked in thyme-scented cream until golden and bubbling — the best use for a summer glut of squash.
Nutrition per serving
⅔ cup- Net carbs
- 5.2g
- Calories
- 218kcal
- Protein
- 9.2g
- Fat
- 18g
- Total carbs
- 7 g
- Fiber
- 1.7 g
Calculated from USDA FoodData Central values for each ingredient (optional ingredients excluded). Brands vary — check your labels if you track closely.
Ingredients
Provençal tian (no cream): Zucchini and tomato slices stood up in alternating rows and roasted with olive oil, garlic and thyme, then finished with parmesan. Lighter, and great at room temperature.
- Soften the onion and garlic in 1 tablespoon of the oil and spread them over the bottom of the dish; skip the cream.
- Stand the zucchini and tomato slices upright in tightly packed alternating rows, tuck in the thyme, drizzle with the remaining oil and season with pepper.
- Bake uncovered for 40–45 minutes, until the vegetables are tender and browned at the tips, scattering the parmesan over for the last 10 minutes.
With Italian sausage: Browned Italian sausage layered between the zucchini makes it a hearty, lasagna-like dinner casserole.
- Before the onion, brown the sausage in the skillet for 6–8 minutes, breaking it up, until no pink remains (160°F/71°C). Lift it out, pour off excess fat and cook the onion in the butter as written.
- Scatter the sausage over each zucchini layer along with the onion.
-
½ cup heavy creamleave out -
¾ cup Gruyèreleave out - Also add
- Also add
Estimated cost $11.14 for 6 servings ($1.86 each) · how we estimate
Instructions
-
Toss the zucchini slices with the salt in a colander set over a bowl and let them drain for 20–30 minutes. Spread them on a clean kitchen towel, roll it up and press firmly to blot away as much moisture as possible.
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Meanwhile, heat the oven to 400°F (200°C) and butter a 2-quart (2 L) baking dish.
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Melt the butter in a skillet over medium heat and cook the onion 5–6 minutes, until soft and lightly golden. Add the garlic for 30 seconds, then pour in the cream with the thyme, nutmeg and pepper and bring just to a simmer. Take it off the heat.
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Arrange half the zucchini in overlapping rows in the dish. Lift half the onion out of the cream and scatter it over, then a third of each cheese. Repeat with the remaining zucchini, onion and another third of each cheese, then pour the cream evenly over everything.
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Top with the last of the cheeses. Bake 30–35 minutes, until bubbling at the edges and deep golden on top, and the zucchini is tender when pierced with a knife.
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Rest 10 minutes before serving so the juices settle and thicken.
Tips for success
-
Salting and blotting the zucchini matters most. Zucchini is about 95% water, and unsalted slices flood the dish and thin the cream to a puddle. - Slice evenly — a mandoline makes it quick — so the layers cook at the same rate. Using half yellow squash looks pretty and tastes the same.
- Serve with roast chicken or steak bites. For a crunchy top, scatter pork rind "panko" over the cheese before baking.
Nice to have, not needed
- A mandoline makes quick, even slices — a sharp knife works if you take your time.
Storage & meal prepMeal-prep friendly
- Keeps 3 days in the fridge
- Doesn’t freeze well
Reheat: Reheat covered at 350°F (175°C) for about 15 minutes, or microwave portions for 1–2 minutes.
Refrigerate up to 3 days and reheat, covered, at 350°F (175°C) for about 15 minutes. Not suitable for freezing — the zucchini turns watery.
Variations
2 variations, each with its own ingredients and macrosProvençal tian (no cream)
VeggiesZucchini and tomato slices stood up in alternating rows and roasted with olive oil, garlic and thyme, then finished with parmesan. Lighter, and great at room temperature.
- butter → extra-virgin olive oil
- + 4 medium plum (Roma) tomatoes
- no heavy cream
- no Gruyère
5.7 g net · 125 kcal · 4.8 g protein · 8.9 g fat · ≈$1.41 per serving (+0.5 g net carbs vs the original)
With Italian sausage
ProteinBrowned Italian sausage layered between the zucchini makes it a hearty, lasagna-like dinner casserole.
- + 8 oz Italian sausage
6.3 g net · 327 kcal · 15 g protein · 27 g fat · ≈$2.24 per serving (+1.1 g net carbs vs the original)
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