In a bowl, combine the Greek yogurt, minced garlic, olive oil, oregano, paprika, salt, and pepper. Add the sliced chicken and toss to coat. Cover and let marinate in the fridge for at least 30 minutes (or up to overnight for more flavor).
Heat a non-stick skillet over medium-high heat. Add the marinated chicken and cook for about 8-10 minutes, or until the chicken is cooked through and has a nice golden-brown color.
While the chicken is cooking, dice the cucumbers, tomatoes, and thinly slice the red onion. Set aside.
In a dry skillet or oven, warm the whole wheat pita breads for a few minutes until they are pliable and slightly toasted.
Place a generous amount of cooked chicken on each warm pita. Top with diced cucumbers, tomatoes, red onion, and crumbled feta cheese.
Sprinkle fresh parsley on top for an extra burst of flavor and color. Roll up the pita around the filling, and serve immediately while warm.