Preheat the oven to 200 degrees Celsius and line a tray with baking paper.
For the marinade add the oil, balsamic vinegar, garlic cloves, oregano, rosemary, salt and pepper to a blender and blend well.
Wash mushrooms and zucchini and cut into bite-sized pieces. Mix the vegetables with the marinade and spread on the baking tray.
Bake for 20 minutes, then turn off the oven and leave the veggies the hot oven for another 60 minutes; this way the veg really soak up the marinade!