Whisk teriyaki sauce, garlic salt, and pepper together in a bowl.

Place pork chops onto a deep plate. Pour 1/2 cup of the teriyaki mixture over chops; flip chops a few times to coat. Cover and marinate in the refrigerator for 30 minutes. Set remaining 1/4 cup marinade aside for cooking.

When ready to cook, remove chops from marinade and shake off excess. Discard remaining marinade.

Heat oil in a large skillet over medium heat. Place chops into the hot skillet; cover and cook until browned, about 15 minutes. Flip and continue to cook, covered, until no longer pink in the center, about 10 minutes. An instant-read thermometer inserted into the center should read at least 145 degrees F (63 degrees C).

Pour in the reserved 1/4 cup teriyaki mixture. Cover and simmer for 5 more minutes.