In a large skillet, heat the olive oil over medium heat. Add the garlic and onion. Saute for about 2-3 minutes or until softened.
Add the sliced eggplant, zucchini, bell pepper, and mushrooms to the skillet. Cook for 5-7 minutes until the vegetables are slightly tender. Add dried basil, oregano, salt, and pepper. Add the tomato sauce and mix well.
Transfer the vegetable mixture to a casserole dish and spread it evenly.
Bake in the preheated oven for 20-25 minutes or until the vegetables are tender and the top is lightly browned. Garnish with fresh basil before serving.
Notes
Peeling eggplant is optional and depends on your preference. The skin adds a slightly chewy texture, it but can also be bitter, especially in older eggplants. If you prefer a smoother texture or find the skin too tough, feel free to peel it before cooking.