Zucchini, Tomatoes, and Onions

1 T oil
4 medium zucchini, sliced
4 tomatoes, sliced
2 onions, diced
1 avocado, diced
basil
salt and pepper

In an oiled casserole dish, combine the zucchini, tomatoes, and onions in layers.  Sprinkle with olive oil, salt and pepper.  Bake at 375 for about 30 minutes, until zucchini is cooked.  Top with avocado and sprinkle with dried basil.