Add the chicken pieces to the bottom of the slow cooker.
Layer the chopped artichoke hearts and spinach over the chicken.
Scatter the cream cheese cubes, 1 cup of the mozzarella, the Parmesan, minced garlic, salt, pepper, and oregano on top.
Stir everything together until the ingredients are evenly distributed.
Cover and cook on low for 5 hours, or until the chicken is fully cooked and tender.
Stir the mixture once more, then sprinkle the remaining 1/2 cup of mozzarella over the top.
Cover again and cook for 15 more minutes until the cheese melts.