Wash the zucchini and cut into one centimeter thick slices, add to the bowl. Wash the peppers, cut into quarters, core and cut the quarters into approx. Three centimeter strips and add to the bowl. Peel the onions and cut into quarters with the stalk so that they stick together, add the pepperoni and zucchini.
Season the vegetables well with salt, pepper, marjoram, thyme and sage. Add the olive oil, then mix the whole thing very well. Put the mixed vegetables in an oven-safe dish, place the rosemary sprigs on top and cover the dish with silver foil. Then bake covered in the middle of the oven for 15 minutes, remove the foil after the 15 minutes, raise the temperature of the oven to 180 degrees and bake again for 15 to 20 minutes.