Preheat oven to 400°. Cut the spaghetti squash in half lengthwise and scoop out the seeds and ribbing. Drizzle the inside of the spaghetti squash with olive oil and sprinkle with salt and pepper. Place squash on baking sheet and bake for 30-40 minutes. Using a fork, scrape out the insides of the squash and set aside. Brown ground beef and then mix with Ragu sauce. In a 9x13 pan, layer squash, ground beef and sauce mixture and then cheese. Place pan in the oven and bake until the cheese is melted.