In a bowl large enough for tossing salad, add diced chicken breast.
Chop the romaine and add to salad bowl. Toss in the cucumber, olives and red onion and set aside.
In a sealable jar or container with a lid, combine red wine vinaigrette, Greek seasoning and crumbled feta cheese. Seal lid and shake vigorously.
Pour dressing over salad and toss to combine. Divide among chilled salad plates and garnish with extra crumbled feta cheese and sliced tomatoes.