Preheat oven to 350 F.

To prepare squash shell, scoop the flesh from each butternut squash half, leaving about 1/2 inch of flesh with the skin. Chop the flesh into small dice and set aside. Boil squash shells in rapidly boiling water for 3 minutes. Drain and place upside down on a baking sheet. Set aside until ready to use. If cooking in a casserole dish, peel both squash and chop flesh into small dice.

Heat oil in a large saucepan over medium heat. Add ham, onion, green pepper and diced squash and sauté 3 minutes. Add sage, salt and pepper and stir to coat. Add chicken broth and bring to a boil. Gradually add instant brown rice and return to a boil. Reduce heat and simmer, covered, for 10 minutes, until liquid is absorbed. Remove from heat and let stand 10 minutes. Add grapes and toss to combine.

Spoon rice mixture into halved squash (making a mound on top of squash) and transfer stuffed squash to a foil-lined baking sheet. Or spoon rice mixture into a 4-quart casserole dish. Sprinkle feta cheese over top. Bake 30 to 35 minutes, until squash is tender and cheese is golden. Serve warm or room temperature.