Preheat oven to 375.

Place squash halves, cut side down, on a baking sheet. Bake for 30 minutes, then remove from heat.

Meanwhile, heat olive oil in a saute pan. Cook onions over medium heat until lightly browned. Add celery and saute for several more minutes.

Remove onion/celery mixture from heat and add to a large bowl. Add the rice, pecans, raisins, cinnamon, cloves, salt and pepper. Mix well.

Spoon out the cooked squash, leaving some squash in the shells. Press rice mixture evenly into each squash cavity.

Cover with aluminum foil and bake for 20 minutes. Remove the foil and cook until tender, about 10 minutes.