Preheat the oven to 210°C/190°C fan
Chop the onion, courgette and lemon. Add to a baking tray with the potatoes.
Drizzle with olive oil and sprinkle over some salt and pepper. Mix well with your hands.
Pat the chicken thighs dry with some kitchen roll. Nestle them in between the potatoes and veg and sprinkle each with some salt and pepper.
Put in the preheated oven for 20 minutes.
Once the tray bake is in the oven, mix all ingredients for the lemon and garlic marinade together in a bowl.
After the 20 mins of baking, pour over the lemon and garlic marinade and return the tray to the oven for another 25 minutes.
Garnish with some fresh parsley (optional) and serve.