Preheat the oven to 400°F. Slice the spaghetti squash in half vertically. If you're having a hard time cutting it, score it with a knife and microwave for a few minutes. Alternatively you could slice into 1 1/2" circles. Then scoop out the seeds with a spoon.
Brush the insides with olive oil and then sprinkle with salt and pepper. Bake for 15 minutes. Then flip upside down (so the outer shell faces up) and bake another 20-30 minutes, or until the inside easily comes up with a fork.
Remove pan from oven and allow to cool on pan for 5 minutes. Then take a fork to scrape the strands up from the center.
Enjoy with butter, parmesan cheese or your favorite marinara.