Preheat the oven to 400°F and coat the bottom of a baking dish with olive oil.
Wash and dry the vegetables. Slice the tomatoes and red onion and set aside.
Peel the potatoes. Slice the potatoes, zucchini and eggplant thinly and set aside.
Add half of the tomatoes and onions to the bottom of the baking dish. Season with salt, pepper and oregano.
Top with eggplant, zucchini and potato slices. Add some more salt, pepper and oregano.
Finally, add the remaining half of the tomatoes and onions and add the remaining spices.
Drizzle the olive oil all over the vegetables and shake the dish just a little bit to make sure all the vegetables are smothered with olive oil.
Cover the dish with a piece of aluminum foil and tent it so it doesn't touch the vegetables.
Bake in the oven for 40 minutes. Uncover and bake for another 30 to 40 minutes until the potatoes are fully cooked. If the vegetables are getting too charred, cover with aluminum foil again.
Top with chopped parsley and serve warm.