Cook pasta according to package directions. Drain pasta; rinse with cold water. Drain again.
In a large mixing bowl combine cooked pasta, cucumber, red onion, and olives. Toss lightly to mix.
For dressing, in a screw-top jar combine oil, lemon juice, oregano, mint, and pepper. Cover and shake well. Pour dressing over pasta mixture. Toss to coat. Cover and chill for 4 to 24 hours.
If desired, line individual salad plates with lettuce. Spoon pasta mixture onto the lettuce-lined plates. Drain tuna and break into chunks. Arrange tuna and feta cheese on top of the pasta mixture. Garnish with cherry tomatoes. Makes 4 main-dish servings.