Pour olive oil into a large pot over high heat. Add onion and garlic and saute for 2 minutes. Reduce heat and add tomatoes, eggplant, zucchini, bell pepper, tomato sauce, herbes de Provence, salt, and pepper. Stir in wine, cover, and simmer for 10 minutes. Uncover and simmer until vegetables are just tender, 12 to 15 minutes. Leave ratatouille warm in the pot until ready to use.

Preheat the oven to 425 degrees F (220 degrees C). Arrange pepper halves, cut-sides down, in a 2-quart baking dish.

Bake in the preheated oven for 10 minutes.

Turn peppers so cut sides face up. Mix 2 cups ratatouille with 1/2 cup Italian cheese blend; spoon into pepper halves. Cover loosely with foil and bake until peppers are tender and filling is heated through, about 25 minutes.

Uncover peppers; sprinkle with remaining cheese. Continue baking until cheese is melted, about 5 minutes more. Garnish with parsley and top with black pepper.