Slice the tomatoes into large wedges or chunks.
Slice the cucumber into rounds or half-moons, and thinly slice the red onion.
In a large mixing bowl, combine the tomatoes, cucumber, red onion, and Kalamata olives.
Place the block of feta cheese on top of the vegetable mixture.
In a small bowl, whisk together the olive oil, red wine vinegar, oregano, salt, and pepper.
Drizzle the dressing over the salad and toss gently to combine.
Serve immediately, or allow the flavors to meld for a few minutes before serving.