Preheat oven to 375 degrees. Saute' onion in oil. Add Rice. Saute' 2-3 minutes, stirring well. Transfer to a 1 1/2 quart casserole. Dissolve bouillon cubes in water and add sage. Pour over Rice. Place spinach on top of Rice. Bake covered at 375 degrees for 45 minutes or until liquid is absorbed. When done, gently stir spinach into rice.