Preheat the oven to 350ºF. Coat a large baking dish with cooking spray or butter. Set aside.
In a large skillet, melt butter over medium heat.
Add onion, carrot, celery, and 1 tablespoon sage. Cook, stirring frequently, until the vegetables begin to soften, about 7 minutes.
Add the garlic, thyme, and salt and pepper to taste. Cook, stirring, 1 minute.
Add the vegetable stock and remove from the heat.
Pour the stuffing cubes into the prepared baking dish and add the remaining 2 tablespoons of fresh sage. Pour the stock and vegetable mixture over the stuffing cubes. Stir well to coat.
Bake 45-60 minutes, stirring once, until the stuffing is beginning to crisp on the edges.
Video
Notes
Tips for customizing the best vegetarian stuffing recipe
If you prefer softer stuffing like you would get in a cooked turkey, add an additional ½ - 1 cup more vegetable broth
Use whatever herbs you have on hand such as parsley or rosemary
Swap the packaged stuffing cubes for a stale loaf of bread, cubed (try keep it to 12 ounces)
Follow the instructions above to make this vegan or gluten-free
Add crumbled bits of vegetarian sausage, seitan, or tempeh for extra protein and flavor