Why is my joint burnt on the outside and raw in the middle?

Every roast has a temperature gradient from the surface to the centre. The question is only how steep it is. The drawing shows the same joint at two oven temperatures — the shape of that curve is what decides whether you get an even roast or a burnt shell around a cold core.

Step by step

1. See the mechanism clearly.Meat is a poor conductor of heat. The surface reaches oven temperature quickly; the centre lags by a long way. The hotter the oven, the steeper the gradient, so the surface can be at 200°C while the centre is still at 40°C. Thickness makes this worse, roughly as the square — a joint twice as thick takes far more than twice as long.
2. Check your oven's real temperature first.An oven running 20°C hot turns a manageable gradient into a burnt one, and dials are frequently wrong. An oven thermometer sitting on the middle shelf answers this permanently and costs very little. Do this before changing anything else about your method.
3. Use two stages, in the right order.Either a short blast at 220°C for 15–20 minutes and then down to 160–170°C for the rest, or the reverse — the whole cook at 140–150°C and a final blast at the end. The second is better for evenness, because the joint spends its long phase in a gentle oven and the browning happens when the middle is nearly there.
4. Match the oven temperature to the thickness.A thin, flat or butterflied joint tolerates a hot oven because the centre is close to the surface. A thick compact joint, a rolled joint, or anything over about 10cm through needs a low oven and time. Judge by how far the heat has to travel, not by weight.
5. Cover the joint or shield the parts running ahead.Foil over the surface stops radiant heat from the element hitting it directly and holds moisture against it, so the surface stays below 100°C and cannot burn. Take the foil off for the last stretch to build colour once the middle has caught up.
6. Use a probe and stop guessing.The gradient means the outside tells you nothing about the middle. A leave-in probe shows you the centre temperature climbing in real time, so you find out about a problem in the first hour rather than at the table. This is the single fix that prevents recurrence.
7. Rescue what you have.Cut the joint in half or into thick slices, cover with foil, and return it to a moderate oven at 160°C until the centre reaches your target — a much shorter distance to travel once the mass is halved. Trim off anything genuinely burnt, because burnt fat tastes bitter and will spoil the gravy.

Tips

• A reverse sear applies exactly this reasoning to a steak: low oven first for evenness, hard sear last for crust. It is the same fix scaled down.
• Fan ovens brown faster than conventional ones at the same dial setting. If a recipe does not specify, drop about 20°C for a fan oven.
• A joint sat directly on the tin base burns where it touches. A rack or a bed of vegetables lifts it into the air where heat is even.
• Very large joints have the steepest gradients of all, which is why a big turkey is so hard to cook well. Spatchcocking or jointing removes the problem rather than managing it.

Common mistakes

• Turning the oven up because it is taking too long — It makes the gradient steeper, so the outside burns faster while the middle is barely affected. When a joint is behind, give it time or lower the temperature and give it more.
• Judging by the crust — A deeply browned surface says the surface has been hot, and nothing at all about the centre. This is exactly the situation a probe exists for.
• Cooking a rolled and stuffed joint at roasting-joint temperatures — Stuffing is dense and insulating, so the effective thickness is much greater than it looks. These joints need a lower oven and longer.

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