Using a sharp
knife, slice tops off tomatoes, reserving tops. Remove and discard
tomato seeds and pulp using a teaspoon. Cut onion into thin wedges.
Julienne - cut into match-stick lengths pepper, cucumber and feta.
Combine onion, pepper, cucumber, feta and olives in a bowl. Place
oregano, olive oil, vinegar and pepper in a screw-top jar. Shake well to
combine. Pour over vegetables and gently toss to coat. Spoon filling
into tomato shells.