Drain artichokes in a colander. Put into large bowl. Mash well with hands. Add mayonnaise, cheese and garlic powder. Using hands, mix well.
Cut the top off of the bread. Use hands to hollow out the loaf being careful not to put holes in the bottom or sides. Save the bread cubes for dipping later. (Put in plastic bag to keep fresh) Put artichoke mixture in hollowed out bread. Replace top of loaf. Wrap well in aluminum foil. *you may refrigerate the loaf at this point until ready to bake.
Preheat oven to 325f. Place wrapped loaf on a baking sheet. Bake about one (1) hour until heated through. Use the leftover bread for dipping. You should also invite guests to break apart the bread "bowl" and use for dipping.