Preheat oven to 350°F (175°C). Grease a 9x13-inch baking dish.
Toast bread cubes in the oven until lightly golden. Set aside.
In a skillet, melt butter. Sauté onion, celery, and garlic until soft and fragrant. Add thyme, sage, and parsley.
In a large bowl, combine toasted bread, sautéed vegetables, and oysters (with liquor).
Whisk eggs into chicken stock. Pour over bread mixture and toss until evenly moistened. Season generously with salt and pepper.
Transfer mixture to prepared baking dish. Cover with foil and bake 30 minutes. Remove foil and bake another 20 minutes until the top is golden and crisp.