Preheat oven to 250°F. Cut or tear the bread into 1-inch cubes. Spread cubes on a large baking sheet and bake for 40–60 minutes, stirring once or twice, until dried out. Cool completely.
Raise oven to 350°F. Heat the oil in a large skillet over medium heat. Add onions and celery and cook 8–10 minutes until softened and lightly browned.
In a large bowl, mix the bread cubes with the cooked vegetables, parsley, sage, and rosemary.
In a small bowl, whisk together eggs, broth, salt, and pepper. Pour over the bread mixture and toss gently until evenly coated.
Butter a 9x13 baking dish with 2 tablespoons butter. Spread the stuffing mixture into the pan and dot the top with the remaining butter.
Cover loosely with foil and bake for 30 minutes. Remove foil and bake another 15–20 minutes until the top is golden brown and crisp and the center is hot.