Oven-baked fish
The short answer
Bake fish at 180 to 200C for 12 to 20 minutes depending on thickness, until the flesh is just opaque and flakes cleanly. A reliable rule is about 10 minutes per 2.5cm of thickness at 200C. A thin fillet needs 12 minutes and a thick loin or a small whole fish closer to 20.
Step by step
1. Heat the oven to 200C fan 180C, gas 6. A hot oven cooks fish before it dries. 2. Line a tray with parchment or oil it lightly so the fish lifts off cleanly. 3. Pat the fish dry, brush with oil and season with salt and pepper. Add lemon, herbs or a knob of butter on top. 4. Bake by thickness, skin-side down for fillets:
- Thin fillets up to 2cm: 10 to 12 minutes.
- Medium fillets 2 to 3cm: 12 to 16 minutes.
- Thick loins over 3cm: 16 to 20 minutes.
- Whole fish around 500 to 600g: 20 to 25 minutes.
5. To keep delicate fish moist, bake it in a parchment parcel (en papillote) with a splash of wine or lemon and aromatics. The steam trapped inside cooks it gently. 6. Check for doneness. The flesh should be just opaque through the thickest point and pull apart cleanly, reading 55 to 60C on a probe. For whole fish the flesh lifts cleanly from the backbone. 7. Rest for a couple of minutes before serving.
Which fish it suits
Baking suits almost everything. Firm white fillets like cod, haddock, pollock and hake hold together well. Salmon and trout stay moist. Whole fish such as sea bass and sea bream roast beautifully on the bone and carry more flavour. Thick cuts like monkfish and halibut take the higher end of the time.
Thin flat fish fillets cook fast and can dry in an open tray, so a parchment parcel protects them. Smoked haddock bakes gently and pairs well with a splash of milk in the parcel.
Tips / common mistakes
- Use the 10 minutes per 2.5cm rule and measure the thickest point.
- Do not bake fish cold from the fridge if you can help it, since 10 minutes out takes the chill off and helps it cook evenly.
- A parcel keeps lean fish moist and makes a light sauce from its own juices.
- Skin-side down protects the flesh and lets the skin take the heat of the tray.
- The usual mistake is leaving it in too long. Pull it at just opaque, as it keeps cooking off the heat.
Frequently asked questions
What temperature should I bake fish at? Between 180 and 200C. A hotter oven at 200C cooks fillets quickly and keeps them moist, while 180C suits gentle parcel cooking and larger whole fish.
How long does fish take to bake? Around 10 minutes per 2.5cm of thickness at 200C. That is 12 minutes for a thin fillet, up to 20 for a thick loin and 20 to 25 for a 500 to 600g whole fish.
Do you cover fish when baking? Only if you want it gentle and moist. A parchment or foil parcel traps steam for delicate fish. Leave it uncovered if you want the top to colour.
Can you bake fish from frozen? Yes. Bake at 200C and add roughly 50 percent to the time, cooking it through to just opaque. Whole fish and thick cuts are better defrosted first for even cooking.
How do I know when baked fish is done? The flesh turns from glassy to just opaque and flakes cleanly with a fork. On a probe the thickest point reads 55 to 60C.
