Preheat the oven to 400 F. Thinly slice the yellow onion. Slice the eggplant, zucchini, yellow squash, and tomatoes into ⅛-inch thick slices. Cut any pieces with a larger diameter into half-rounds.
Pour the marinara in the bottom of a large casserole dish. Sprinkle the sliced onions over top.
Begin to line up the sliced eggplant, zucchini, squash, and tomatoes into the dish, standing on their sides, and in an alternating pattern until all of the pieces are used up. Drizzle the olive oil over the vegetables, then sprinkle the basil, oregano, salt, and pepper over top.
Transfer the dish to the oven and roast the vegetables for 40 minutes. After 40 minutes, remove the dish from the oven and sprinkle the shredded mozzarella over top. Return the casserole dish to the oven for five minutes, or until the cheese is melted and creamy.
After roasting, sprinkle the chopped parsley over top, then serve.
Notes
Used with permission from Beth Moncel at Budget Bytes