Preheat the oven to 350°F. Coat a 1-quart baking dish with butter. Set aside.
In a large bowl, beat together the cream cheese, sour cream, mayonnaise, parmesan, mozzarella, garlic, salt, and pepper until smooth.
Stir in drained artichoke hearts and spinach. Add mixture to a prepared baking dish and spread evenly. Bake for 20 minutes, or until heated through and melted.
Serve warm with your choice of chips or crispy bread. Enjoy!