Combine the olive oil, lemon juice, garlic, oregano, chilli and salt and pepper in a bowl. Whisk until well combined. Use a little of the marinade to brush over both sides of the haloumi. Add the mushrooms to the remaining marinade and stir to coat all the mushrooms. Cover and refrigerate both the mushrooms and haloumi for 30 minutes.
Preheat a greased barbecue plate on medium-high. Barbecue the mushrooms for 5 minutes, turning occasionally until just tender. Remove to a large bowl. Barbecue the haloumi for 1-2 minutes each side or until golden and warmed through. Add to the warm mushrooms.
Add the tomatoes and spinach to the mushrooms and cheese, toss gently to combine. Arrange on serving plates, drizzle with a little extra virgin olive oil and serve with barbecued bread.