Bring a large pot of salted water to a boil. Preheat the oven to 400 degrees F.
Cut the stems from the artichokes to leave a neat, flat base. Lay each artichoke on its side, and cut away the upper third with a sharp knife. With kitchen shears, remove the prickly leaf tips from each remaining leaf. Rub the cut sides and bottom with a lemon slice, squeezing lemon juice onto the cut areas and set aside.
Place the prepared artichokes, lemon slices, crab boil and bay leaves in the boiling water and simmer, partially covered, until the bottom is tender and can be pierced with a sharp knife and an outer leaf pulls out easily, about 25 minutes.
Heat the butter in a small skillet over medium heat. Add the onions and cook until softened, about 4 minutes.
To the onion pan, add the garlic and oregano and continue to cook for 30 seconds.
Remove from the heat and stir in the bread crumbs, lemon zest, Parmesan, and 1/4 cup of the olive oil. Mix well and adjust seasonings with salt and freshly ground black pepper.
Drain the artichokes upside down in a colander.
When the artichokes are cool enough to handle, press the leaves gently back so that the artichoke opens to reveal the inner choke and prickly leaves. Pull out the cone of undeveloped white leaves and gently scrape out the choke with a spoon so as not to damage the heart. Gently pull the leaves outward from the center until the leaves open slightly.
Fill the artichoke cavities with bread stuffing, and pack a little bit into the space between the leaves.
Place the artichokes in an earthenware baking dish and drizzle the tops with the remaining 2 tablespoons of olive oil.
Pour 1/2 cup of water into the bottom of the dish and place in oven. Bake until the artichokes are golden brown and the bread crumbs develop a nice crust, about 10 to 15 minutes.
Transfer to a serving plate, drizzle with some olive oil and sprinkle some grated Parmesan. Serve with additional lemon wedges.