1. Heat oven to 350 degrees F. Place squash halves cut-side down on a rimmed dish. Add 2 cups water to dish and bake at 350 degrees F for 40 minutes.
2. Meanwhile, cook bacon in a large nonstick skillet over medium heat for 4 minutes. Add onion and apple. Cook an additional 4 minutes, stirring occasionally.
3. Stir in ground beef. Cook, breaking meat apart with a wooden spoon, 5 minutes. Add brown sugar, pumpkin pie spice, sage, salt and pepper. Cook 1 minute. Remove from heat and stir in bread crumbs.
4. Drain water from baking dish and flip over squash. Spoon meat mixture into squash halves. Return to oven and bake at 350 degrees F for 20 minutes. Serve warm.