Line the baking sheet with foil, and spray the oil over the foil
Cut the squash in 2 halves, scrape out the seeds and the fiber out of each half. Spray oil over the cut sides and inside of the squash. Place the squash on the prepared baking sheet cut side down.
Bake for about 40 minutes. Remove it from the oven when it's cooked through and soft. You can check by pulling the baking sheet out of the oven and piercing the squash with the fork - it should be soft.
Remove squash out of the oven. Allow it to cool right on the baking sheet. Flip the squash so that cut side faces up – that will speed up the cooling. Cool for about 30 minutes.
After squash cools, scrape squash with a fork to remove flesh in long strands and transfer to a bowl. Let it cool.
Note: Cooked spaghetti squash can be refrigerated for up to 5 days.