First, make the dressing. Combine vinegar, lemon juice, oregano, and olive oil. Season with salt and pepper to taste. Place in the fridge until needed.
Cut all the ingredients into small pieces. Add cucumber, bell pepper, tomatoes, onion, and olives to a bowl. Drizzle with the salad dressing and toss to combine. Season with salt to taste. Sprinkle the feta cheese and oregano on top.