Peel the opo squash and cut in half lengthwise. Remove the seeds. Cut into 1-inch pieces.
Heat the olive oil in a skillet. Add the onion and cook for 3-5 minutes, until translucent. Add the garlic and cook for 30 seconds more. Add the opo squash, season with Italian seasoning, salt, and pepper, and sauté for 10-12 minutes, until the squash is tender.
Preheat the oven to 425°F.
Peel the opo squash and cut in half lengthwise. Remove the seeds. Cut into 1-inch chunks.
In a large bowl, toss the opo squash chunks with the olive oil, salt, pepper, and Italian seasoning.
Arrange in a single layer on a parchment-lined baking sheet. Sprinkle with the Parmesan cheese.
Bake 25-30 minutes, stirring after 15 minutes. Broil 1 minute, if desired.
