MIX dressing and oregano; cover. Refrigerate until ready to use.
FOR each serving: Place 3 cups salad greens in carry-out salad container. Top with 1/2 cup tuna, 3 tomato wedges, 1/4 cup cucumbers, 1/4 cup olives and 1 Tbsp. cheese.
POUR 3 Tbsp. of the dressing mixture into portion cup; seal lid. Place cup in salad container; close container lid. Refirgerate until ready to serve.