Preheat your oven to 400°F (200°C) to prepare for roasting the vegetables.

Wash and chop the zucchini, tomatoes, and red onion into uniformly-sized pieces.

Spread the chopped vegetables across a large baking sheet. Drizzle with olive oil, sprinkle with oregano, salt, and pepper. Toss until evenly coated.

Arrange the vegetables in a single layer on the baking sheet for even cooking.

Roast in the oven for about 30 minutes, stirring halfway through to promote even browning.

Once roasted, remove from the oven and sprinkle feta cheese over the hot vegetables if using.

Let the roasted vegetables cool slightly before serving.