Preheat oven to 350 degrees.
Cut the butternut squash in half lengthwise, scoop out the seeds, and place cut side up on a baking sheet lined with aluminum foil.
Brush cut side of the squash with olive oil and sprinkle with salt and pepper. Cover with a sheet of aluminum foil and bake for 45-60 minutes or until tender when poked with a fork.
In a medium sauce pan, combine the quinoa and vegetable broth. Bring to a simmer and cover. Cook about 15-20 minutes or until broth is absorbed. Set aside.
Put the brussels sprouts in a food processor and process until finely chopped/shredded.
In a skillet, melt the butter. Add the chopped onion, sage, and brussels sprouts. Cook over medium-high heat, stirring frequently until brussels sprouts begin to brown and onion is translucent.
Combine the quinoa, sprout mixture, olives, balsamic, and feta.
Scoop out the flesh of the butternut, leaving about 1/3-1/2 inch of pulp in the skin. In a small bowl, mash the scooped out squash well and then add the the quinoa. Stir until combined.
Spoon quinoa mixture into the hollowed out portion of the butternut squash. Bake for another 10 minutes and serve.