4 (6-ounce) farm-raised catfish fillets |
1/2 teaspoon greek seasoning |
1/4 teaspoon garlic powder |
8 (1/8-inch-thick) slices lemon (about 1 lemon) |
1 small onion, thinly sliced and separated into rings |
2 small zucchini, thinly sliced |
1 cup grape tomatoes, halved |
8 kalamata olives, pitted and coarsely chopped |
1 tablespoon chopped fresh oregano |
4 teaspoons olive oil, divided |