Combine the olive oil, lemon juice, salt, oregano, garlic powder, and pepper in a large resealable bag. Add chicken cubes, mix well, and allow to marinate in the refrigerator 3 hours or overnight.
Pour the chicken and marinade into a frying pan over medium-high heat. Cook until the chicken is no longer pink. Stuff each half of the pocket bread with chicken, onion, tomato, and yogurt; serve while still hot.
