Why are my roasted vegetables soggy instead of crispy?

Browning needs dry heat. Vegetables are full of water, and when they heat up, that water comes out as steam. If the steam can escape, the surfaces dry and start to colour. If it can't, the vegetables simmer in their own vapour and come out soft, pale and a little sad. Every fix below is a way of letting the steam go.

Work through this list in order. Usually the first or second item is the culprit.

1. Is the tray crowded?

The most common cause by a distance. Pieces packed shoulder to shoulder trap steam between them. Each piece needs a little air around it, in a single layer, no stacking.

If everything doesn't fit, use two trays. It feels extravagant and makes all the difference. Swap the trays between shelves halfway through if your oven has a hot spot.

2. Were the vegetables wet?

Washed vegetables carry a film of water into the oven, and that water has to evaporate before anything browns. Dry them properly with a clean tea towel. For watery vegetables like courgettes or aubergines, a sprinkle of salt and a rest in a colander first draws out some moisture; pat them dry before oiling.

Frozen vegetables can roast well too, straight from the freezer onto a very hot tray, spread out. More in is frozen veg cheating.

3. Is the oven hot enough?

A moderate oven cooks vegetables through before it browns them. You want a properly hot oven, fully preheated before the tray goes in. A tray that has been heating in the oven gives a head start: the vegetables sizzle as they land.

Fan ovens run hotter and drier than conventional ones and usually brown better; the details are in what the fan setting changes.

4. Too little oil, or too much?

Oil carries heat into the surface of each piece. Too little and the vegetables dry out in patches without browning evenly. Too much and they fry and go greasy, sitting in a puddle. Toss them in a bowl with enough oil to give every surface a thin, glossy coat, then tip them onto the tray. The bowl does a better job than drizzling over the tray.

5. Are the pieces the right size and shape?

Very small pieces burn before they brown evenly; very large chunks steam inside themselves for a long time. Aim for even, medium pieces with at least one flat cut side, and lay that flat side down. That face, in contact with the hot metal, is where the deep colour happens.

6. Did you keep opening the door and stirring?

Every peek lets heat out. Every stir moves a piece away from the hot tray just as it was starting to colour. Leave them alone for a good while. Turn once, when the undersides are properly golden, not before.

7. Did they go soft after coming out?

Roast vegetables soften as they sit, especially if covered or piled in a bowl, because the steam has nowhere to go. Serve them from the tray or spread on a platter, and add dressings, sauces and soft cheeses at the last moment.

Mixed trays

Root vegetables, peppers, onions and courgettes do not finish at the same time. Either cut slower vegetables smaller, or start them first and add the quick ones later. Cherry tomatoes and anything very juicy are best on their own tray, or they flood their neighbours.

Season at the right moment

Salt before roasting is fine for most vegetables, and it helps flavour. Delicate herbs, garlic and cheese burn if they go in at the start; add garlic for the last stretch and herbs after roasting. Finish with a squeeze of lemon or a little vinegar for brightness. For the wider principles of making vegetables taste good, see make vegetables taste good.