Preheat oven to 350 °F. Arrange squash halves cut side down in baking dish or roasting pan. Bake until tender, 25 to 30 minutes.
Meanwhile, make filling. In large saucepan, bring 4 cups water to boil. Add wild rice and 1/2 teaspoon salt. Reduce heat, cover and simmer until rice is tender, about 40 minutes. Drain if necessary.
In another large saucepan, bring remaining 2 cups of water to boil. Add quinoa. Reduce heat and simmer until water is absorbed and quinoa is tender, about 12 minutes.
In large, deep skillet, heat oil over medium heat. Add green onions, celery and sage, and cook, stirring often, until vegetables begin to soften, about 3 minutes. Add dried fruits and nuts and cook, stirring often, until heated through. Using a fork, fluff quinoa and wild rice, then add both to skillet. Add orange juice and mix until heated through. Season with salt.
To serve, remove squash from oven and arrange on serving platter. Spoon filling into each squash cavity and serve.