Preheat the oven to 220°C / gas mark 7. Put the oil in the bottom of two shallow roasting tins, one tablespoon in each. Rub the skin of the chicken in the oil, then turn skin-side up, six pieces in each tin.
Divide the chorizo sausages and the new potatoes between the two tins. Sprinkle the onion and the oregano over, then grate the orange zest over the contents of the two tins.
Cook for an hour, but after 30 minutes swap the top tray with the bottom tray in the oven and baste the contents with the orange-coloured juices.
Recipe from Nigella: Kitchen by Nigella Lawson (published by Chatto & Windus).