Place quinoa and 3/4 cup (175 mL) water in medium saucepan. Bring to a boil then immediately reduce heat to medium-low. Cover and cook 10 min; remove from heat. Let stand 5 min. then uncover and cool.
Meanwhile, in a large bowl, mix feta, tofu, garlic, kale, oregano and cooled quinoa. Blend in egg; season to taste.
Preheat oven broiler, with rack in middle of oven. Using 2 tbsp (30 mL) at a time, shape mixture into 12 egg-shaped "croquettes". Place on foil-lined baking sheet. Broil croquettes about 7 min., turning once, or until golden brown and crispy on edges.
Place three croquettes inside each pita. Top with tzatziki sauce, lettuce, tomato and cucumber.
To make your own tzatziki, seed a medium cucumber into lengthwise ribbons using a vegetable peeler. Finely chop cucumber ribbons, mix with 2 cups (500 mL) plain Greek yogurt, a minced clove of garlic, and season with salt to taste.