In a large pot or 7¼-quart Dutch oven, fry the bacon over medium-low heat until the fat renders and the bacon crisps, 5 to 7 minutes. Add the onion, pepper, carrot and celery, reduce the heat to low, cover, and cook until softened, about 10 minutes. Add the garlic and oregano and sauté for 1 minute.
Add the wine and increase the heat to high. Boil the wine until it reduces by half, about 2 to 3 minutes. Add the 3 bottles of clam juice, the reserved canned clam juices, the potatoes, and bay leaf. Bring to a boil, then reduce the heat to medium-low, and simmer until the potatoes are almost tender, 8 to 10 minutes. Using a wooden spoon, smash some of the potatoes against the side of the pot, then simmer for 5 more minutes.
Add the diced tomatoes (along with their juice), bring back to a simmer, and cook for 5 minutes. Remove the pot from heat, stir in the canned clams and season with salt and pepper to taste; discard the bay leaf. (Chowder can be refrigerated in an airtight container for up to 2 days. Warm over low heat until hot.) Stir in parsley and serve immediately.