In a large saucepan, bring broth to a boil. Stir in orzo; cook over medium heat for 6-8 minutes or until tender. Remove from the heat., In a small skillet, saute onion in oil until tender. Add garlic; cook 1 minute longer. Stir into orzo mixture. Stir in 1 cup cheese, spinach, red peppers, squash, salt and pepper., Transfer to a greased 13-in. x 9-in. baking dish; sprinkle with remaining cheese. Bake, uncovered, at 350° for 20-25 minutes or until heated through.