Mix oregano into salad dressing, set aside. Cut tomatoes in half lengthwise, or dice garden tomatoes. Peel cucumber in strips, leaving some green stripes lengthwise. (For small garden cucumbers or Persian cucumbers you may not need to peel.) Cut cucumbers in half lengthwise, then in slices. Remove seeds from peppers and dice peppers in 3/4 inch square pieces.Dice red onion or cut green onion into 1 inch long pieces. Drain olives and cut in half lengthwise. Cut Feta into cubes about 1/2 inch square. Combine tomatoes, cucumbers, peppers, onions, and olives and toss with desired amount of salad dressing. (You may not need all the dressing.) Stir feta cubes into salad and season with fresh-ground black pepper. The salad can be served immediately, but I like it best when the ingredients can marinate for an hour or two.