Preheat oven to 350°F. Scatter bread cubes on a rimmed baking sheet. Toast until golden brown, tossing once, about 15 minutes. Let cool completely.
Heat oil in a large skillet over medium heat. Add chorizo and cook, breaking up into smaller pieces with the back of a spoon, until browned and cooked through, 8-10 minutes. Add garlic and onion, and cook until soft. Fold in peppers.
Transfer cooked ingredients to a bowl and toss with stock, bread cubes and scallions.
Transfer mixture to a buttered, 3-quart shallow baking dish. Bake until stuffing is hot and the top is golden brown, about 40 minutes.