Add the California grapes, celery, salt, and pepper and continue to cook, stirring occasionally, for another 5 minutes, until soft. Remove from heat and set aside.
In a large bowl, whisk together the vegetable broth, eggs, and Worcestershire sauce. Set aside.
Prepare the candied walnuts. In a small saucepan, add the butter, sugar and chopped walnuts. Stir frequently, until the butter is melted, and the walnuts are well covered. Add walnuts to a parchment-lined baking sheet. Using your hands, spread the walnuts into an even layer and let them set for about 5 minutes.
Tear bread into 1-inch pieces: in a small bowl, tear the small loaf sourdough bread into 1-inch pieces or about 5-6 cups.
Add the bread to the baking dish. Add in the California grapes and celery mixture, 3/4 cup of the candied walnuts, rosemary, and vegetable broth mixture. Mix to combine (*if you find it easier, you can do this in a large bowl and then transfer to the baking dish).
Drizzle the remaining 2 tablespoons olive oil on top and cover with foil.
Bake in the preheated oven for 35 minutes. Pour the remaining 1/3 cup of vegetable oil over the stuffing. Turn the heat up to 425 and bake for another 15 minutes.
Top with the remaining 1/4 cup of candied walnuts and serve.