Heat the oven to 200°C/Fan 180°C/Gas 6. Peel the red onion and slice into wedges. Halve the butternut squash. Scoop the seeds out of one half. Peel and chop it into even, bite-sized chunks.
Peel the sweet potatoes. Slice them into thick wedges. Rinse the pepper and halve it. Scoop out the seeds and white bits. Chop roughly. Rinse and halve the tomatoes.
Tumble the squash, sweet potatoes and onions into a roasting tin. Add a glug of olive oil. Season with salt and pepper. Roast the veg in the oven for 15 mins.
Drizzle the lamb steaks with a little olive oil. Season with salt and pepper. Rub into both sides of them.
Heat a frying or griddle pan over a high heat till it’s smoking hot. Add the lamb steaks to the pan. Fry for 1-2 mins on each side till the steaks start to brown.
Take the veg out of the oven. Add the pepper, tomatoes and most of the oregano. Pop the lamb steaks on top. Roast for 15-20 mins till the veg is tender and the lamb is cooked through - if your lamb leg steaks are thick they will take a little longer to cook.
Spoon your roasted veg onto warm plates. Top with the lamb steaks. Spoon over any juices from the roasting tin. Serve scattered with the rest of the oregano.