Spread bread cubes onto 2 sheet pans in a single layer. Toast at 350°F for 10-15 minutes or until crisp and dried all the way through.
Increase oven temperature to 375°F.
Heat olive oil in a large skillet over medium heat. Add diced celery and onions. Cook until starting to soften, about 5-6 minutes.
Add mushrooms, thyme, sage, and garlic. Cook until tender, about 4-5 minutes. Add salt and pepper.
Transfer veggie mixture to an oiled 7 ½" x 9 ½" baking dish (or similar size that holds 2.75 quarts).
Fold in bread cubes. Add low sodium vegetable broth. Stir to make sure all the cubes are coated. Season with more salt and pepper, if needed. Cover with aluminum foil.
Bake at 375°F for 30 minute. Remove aluminum foil and bake another 10 minutes, or until golden brown.
Notes
You can make this a day or two ahead of time if needed. Just follow all the steps in the recipe, but don't add the vegetable broth or bake it.Place the toasted bread in an airtight container in the pantry. Place the cooked veggies in an airtight container in the fridge. Then on Thanksgiving assemble, add the vegetable broth, and bake it as per instructions.It also tastes great when reheated in the microwave.