At What Temperature and for How Long Should Sliced Zucchini Roast in the Oven?

Sliced zucchini browns at the edges and becomes tender inside when roasted in a preheated oven at 220°C / 430°F for 20–25 minutes. The high temperature speeds up the evaporation of water inside the zucchini, allowing it to brown without becoming mushy. Why use a high temperature? Zucchini consists mostly of water by weight. At a lower temperature (160–170°C / 320–340°F), the water builds up inside before it can evaporate, leaving the vegetable soft and watery, as if boiled. A high temperature such as 220°C / 430°F quickly evaporates surface moisture and allows the edges to brown. How does slice thickness affect the time? Slices about 1–1.5 centimeters thick give the most balanced result. Thinner slices brown and dry out in as little as 15 minutes, while thicker slices may take up to 30 minutes and may not release all their water inside before the outside browns. How can you cook zucchini without it releasing its water? If the slices are lightly salted and left in a colander for 10–15 minutes before going into the oven, the excess water drawn out by the salt can drain away. This reduces the water released in the oven and makes the browning more pronounced. If the slices overlap or are crowded on the baking sheet, steam gets trapped and prevents them from browning properly. Why does how you arrange them on the baking sheet matter? Arrange the slices in a single layer with small gaps between them. If they are crowded, the zucchini cooks in its own steam and stays pale instead of browning. Using a wire rack instead of parchment paper lets air circulate underneath too, helping both sides brown evenly. Should you flip them halfway through? Turning the slices about halfway through helps both sides brown evenly. Unflipped slices brown only on top; the side touching the baking sheet stays steamed and paler. How does the time change in an air fryer? Slices of the same thickness brown in an air fryer at 190°C / 375°F in 12–15 minutes. The air fryer's strong air circulation evaporates water faster than an oven does, noticeably shortening the time. Arranging the slices in a single layer in the basket is just as important. Should zucchini be roasted with or without the skin? Zucchini roasted with the skin on holds its shape better and develops extra texture on the outside. Peeled zucchini softens faster and releases its water a little more easily. If the skin is clean and unblemished, roasting it with the skin on reduces waste and gives more pronounced browning. Toss the zucchini slices with olive oil just before putting them in the oven. If they are tossed too early, the oil and salt can continue drawing out extra water. If using seasonings such as thyme or red pepper flakes, sprinkle them on at the same time as the oil, just before roasting; seasonings added earlier may become bitter at high heat and overpower the zucchini's flavor. This simple sequence visibly improves flavor and browning without adding extra time.