Carefully hollow out the sourdough loaf by cutting off the top and scooping out the insides, leaving a thick shell. Keep the removed bread for later use.
In a medium bowl, combine the chopped spinach, artichoke hearts, cream cheese, sour cream, mozzarella cheese, Parmesan cheese, minced garlic, and dried oregano. Mix until well combined and season with salt and pepper to taste.
Spoon the spinach artichoke mixture into the hollowed bread, filling it generously.
Brush the outside of the stuffed bread with a bit of olive oil for a golden finish.
Place the stuffed bread on a baking sheet and bake in the preheated oven for about 25-30 minutes, or until the bread is golden and the filling is bubbling.
Remove from the oven and let cool slightly. Garnish with fresh parsley before slicing.
Serve the stuffed bread while warm, offering the scooped-out bread as dippers for the creamy filling.