Preheat the oven to 180 degrees Celsius (FAN), gas 6, or static oven 200 degrees Celsius or 400 Fahrenheit.
Chop the zucchini, peppers, and onions in dice the same size; as these vegetables require the same time to cook, cutting them all the same size will bear the best result, as they will also mix well. The vegetables you see in the picture are about 1-inch in size (2.5cm)
Toss the chopped vegetables in a large mixing bowl and season with salt, cracked black pepper, one tablespoon of extra virgin olive oil, and some freshly chopped garlic.
Mix the vegetables well until they are all fully seasoned.
Prepare the baking tray by covering it with a sheet of aluminum foil and lay the vegetables on it, ensuring they are in a single layer.
Put the vegetables on the middle shelf in the oven and roast for 25-30 minutes, or until liked.
Serve and enjoy!