Heat oil over medium-high heat in a large Dutch oven. Add seitan and cook until browned. Set aside.
Add onion and celery to pot; cook until tender, about 5 minutes. Add vinegar and deglaze.
Add butternut squash and broth to pot. Bring to a boil; reduce heat and simmer until squash is tender, about 15 minutes. Stir in kale and bulgur wheat; cook until kale is wilted. Add seitan, salt and pepper.
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