Heat oven to 400 degrees. In a bowl, mix 2 cups cooked wild rice, 1 cup hummus, 1/3 cup chopped toasted walnuts, and 1/3 cup chopped fresh parsley. Season with coarse salt and red-pepper flakes.
In a baking dish, arrange 2 halved small bell peppers (seeds removed) cut sides up. Drizzle with 1 tablespoon extra-virgin olive oil and season with coarse salt and freshly ground black pepper. Divide rice mixture among peppers.
Cover with parchment-lined foil and bake until tender, about 30 minutes. Uncover and cook until topping is slightly crisp, about 10 minutes more. Garnish with more chopped toasted walnuts and parsley.