In a large mixing bowl, combine the diced tomatoes, cucumber, red onion, feta cheese, parsley, and Kalamata olives.
In a small bowl, whisk together the olive oil, red wine vinegar, dried oregano, salt, and pepper until well combined.
Pour the dressing over the vegetable mixture and gently toss until everything is evenly coated.
Let the salsa sit for at least 15 minutes at room temperature to allow the flavors to meld.
Serve chilled or at room temperature with pita chips, grilled meats, or as a topping for salads.