Preheat oven to 350F and line a large baking sheet with foil.
Using a very sharp large knife, cut squash in half lengthwise and scoop out and discard seeds.Drizzle with olive oil and bake 60 to 90 minutes, depending on size of squash until very tender.
Scoop flesh into a large bowl and reserve squash skins. Add butter and let melt, then add Parmesan, garlic, oregano, salt and pepper. Toss until well combined.
Divide mixture among reserved skins and top with cheese. Return to oven and bake another 8 to 10 minutes, or until cheese is melted and bubbly. Enjoy!