Prepare the Squash:
Preheat the oven to 375°F (190°C).
Slice the squash in half lengthwise and use a spoon to scoop out the seeds and some of the flesh, creating a cavity for the filling. Reserve the scooped flesh and finely chop it.
Cook the Filling:
Heat a large skillet over medium heat. Add ground meat and cook until browned, breaking it apart with a spoon. Remove and set aside.
In the same skillet, sauté onion, bell pepper, garlic, and the chopped squash flesh until softened, about 5 minutes.
Return the meat to the skillet and stir in cooked rice or quinoa, Italian seasoning, salt, pepper, and parsley. Mix well and remove from heat.
Stuff the Squash:
Place the squash halves in a baking dish, cut side up. Spoon the filling into each squash, packing it gently.
Sprinkle the tops with breadcrumbs and cheese.
Bake the Squash:
Cover the dish with foil and bake for 20 minutes. Remove the foil and bake for an additional 10 minutes, or until the squash is tender and the cheese is melted and bubbly.
Serve:
Garnish with additional parsley and serve warm.