Preheat the oven to 425° F. Grease a sheet pan or large baking dish with oil or cooking spray.
Brush the inside of the squash with olive oil. Place the squash cut side down on the prepared sheet pan. Bake for 40 minutes until the squash is very tender.
When cool enough to handle, flip the squash over. Using a fork, scrape the flesh to release spaghetti-like strands. Season with salt and pepper.