In a large bowl combine the cream cheese, chopped artichoke hearts, spinach, and mayonnaise. Using a sturdy spoon stir ingredients together until well combined.
Add the mozzarella cheese, feta, Parmesan cheese, garlic powder, and onion salt. Stir to combine.
Transfer dip to a disposable aluminum container, cover, label, and freeze. (SEE BELOW FOR INDOOR BAKING INSTRUCTIONS)
When you are out camping and ready to heat the dip up, remove the cover, and cover with aluminum foil.
Make sure that the fire has a good amount of coals and is burning hot. Place dip on campfire grill. Keep the grill and dip to the side.
The dip will take anywhere from 30-50 minutes to become bubbly and warmed thoroughly. This will greatly depend on the type of cooler you used to store the dip, how frozen the dip still was when you started to cook it, and how hot your fire is.
Keep an eye on the dip and turn the container a few times during cooking. The dip is ready to eat when it is fully warmed and bubbling at the edges.
Carefully remove dip from the fire and stir dip before serving.