Preheat oven to 350°F. Melt butter in large skillet on medium heat. Add squash, celery and onion; cook and stir 15 minutes or until squash is fork-tender
Mix brown and wild rice in large bowl. Stir in vegetable mixture and seasonings. Add stock; toss gently until well mixed. Spoon into lightly greased 13x9inch baking dish. Sprinkle with pecans. Cover with foil
Bake 30 minutes or until heated through.