Quarter the peppers, clean, wash and cut into pieces. Wash, clean and slice the zucchini. Clean, clean and halve the mushrooms. Peel and finely chop the onion.
Heat the oil in a pan, sauté the onion in it and remove it. Fry the bell peppers in the frying oil for approx. 5 minutes, turning them over, and take them out. Fry the zucchini slices briefly on both sides, remove. Add the mushrooms to the oil and fry for about 5 minutes, turning.
Add onions, zucchini and peppers and deglaze with tomatoes. Chop the tomatoes a little bit, simmer for 2-3 minutes. Wash basil and cut into strips except for something to garnish. Stir basil and oregano into the vegetables.
Pour into a greased casserole dish. Grate the cheese and sprinkle over the vegetables. Bake in a preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for approx. 15 minutes until golden brown. Garnish with basil.
Serve with pita bread.