1Heat oven to 375°F. Cut each squash lengthwise in half; remove seeds and fibers. Drizzle cut sides with 3 teaspoons olive oil; sprinkle with salt and pepper. On cookie sheet, place squash, cut-sides down. Bake 35 to 40 minutes until squash is tender at thickest portion when pierced with fork. When cool enough to handle, cut off long ends of squash to within 1/2 inch edge of cavities (peel and refrigerate ends for another purpose).
2Meanwhile, in 1-quart saucepan, heat remaining 1 teaspoon oil over medium heat. Add rice to oil, stirring well to coat. Stir in chicken broth, thyme and bay leaf. Heat to boiling; reduce heat. Cover and simmer 30 to 35 minutes until all liquid is absorbed and rice is tender. Remove from heat; discard thyme sprig and bay leaf.
3In 10-inch nonstick skillet, cook sausage and onion over medium-high heat 8 to 10 minutes, stirring frequently, until sausage is thoroughly cooked. Add mushrooms. Cook 4 minutes or until mushrooms are tender. Stir in cooked rice, spinach and sage; cook about 3 minutes or until spinach is wilted and mixture is hot. Divide sausage-rice mixture between squash halves, pressing down on filling so it forms a slight mound over cavity.