The fresher the vegetables the better this dish will taste. Start with all of the vegetables at room temperature to ensure the best flavor.
Peel the onion and cut in half vertically. Lay the halves flat and cut into segments (like orange segments). Cut each segment into bite-sized chunks and place in a large bowl.Peel the cucumber and cut lengthwise. Scrape out the seeds with a teaspoon. Cut the lengths into half-inch slices and combine with the onion.Remove the stem socket from the tomato, slice into segments and then into bite-sized chunks. Add to the bowl.Sprinkle the vegetables with salt, pepper and oregano. Add olives and Feta and toss lightly to combine.Drizzle with olive oil, toss again lightly and serve.