Preheat the oven to 200 °C (180 °C fan) and line a baking tray with baking paper.
Cut the peppers, courgette and red onion into rough, evenly sized pieces and spread them out on the tray.
Toss the veg with the olive oil, oregano, salt and pepper and roast at 200 °C for 12–15 min until lightly coloured.
Slice the halloumi. Take the tray out, tuck the halloumi in between the veg and scatter over the pumpkin seeds.
Bake everything at 200 °C for another 8–10 min until the halloumi has golden-brown patches and the veg is soft and lightly roasted.
Serve straight from the oven, ideally while still warm, so the halloumi stays browned on the outside and soft inside.
Good to know
A traybake like this is made for relaxed evenings. Little effort, lots of flavour, and at the end everything lands on the plate warm, well-seasoned and golden brown.
Swaps
Halloumi → sheep's or goat's milk feta (milder, also provides protein); pumpkin seeds → walnuts (more omega-3 fatty acids; contains tree nuts); courgette → aubergine (more fibre per serving); olive oil → avocado oil (heat-stable, mainly monounsaturated fats)
Allergens
Contains milk (halloumi). Only partly suitable for small children because of the salt and the firm texture of the cheese; in pregnancy, halloumi is generally fine if it's made from pasteurised milk and heated through well.