Preheat oven to 400°F.
Cut spaghetti squash in half lengthwise (this is easiest with a large chef's knife). Remove the seeds by scraping first with a fork to remove and loosen the big chunks and second with a spoon to scrape well. Alternatively, use a grapefruit spoon to remove the seeds and "guts."
Place spaghetti squash halves facedown on a baking sheet. Bake for 40 minutes at 400°F.
While spaghetti squash is baking, prepare the meatballs. In a large bowl, mix together the egg, parmesan cheese, breadcrumbs, garlic, salt, pepper, milk, oregano and parsley.
Add the ground meat and mix well. (It's easiest to incorporate all the ingredients into the meat by massaging it with your hands rather than using a spoon.) Separate into desired meatball size, generally a 1-1 1/2 inch diameter is good for serving.
Bring 1 1/2 c pasta sauce to a simmer in a non-stick fry pan. Add meatballs. After ~10 minutes, gently flip meatballs. Cook for another 10 minutes or until cooked through thoroughly with internal temperature reaching 165°F. Roll once more in pasta sauce to moisten before removing meatballs from stovetop. Can discard pasta sauce remaining in the saucepan (as it will be a little fatty), or keep for extra topping.
After spaghetti squash has been baked for 40 minutes, remove from oven. Flip spaghetti squash halves right-side up. Scrape the "meat" of the spaghetti squash. It will begin to pull and reveal its "noodles." Place spaghetti squash noodles into a bowl and season with salt and pepper to taste.
Warm remaining 1 1/2 c pasta sauce in the microwave or on the stovetop.
Plate your meal! Top spaghetti squash with meatballs and pasta sauce as desired. (You will probably not want to use the pasta sauce the meatballs were cooked in as it becomes a little fatty after the meatballs are cooked in it. For best results, use the additional pasta sauce that was warmed separately.)
Garnish with fresh basil.