Wash the spaghetti squash and pat it dry. Pierce it several times with a knife or fork.
Place the whole squash in the slow cooker.
Cook on low for 6-8 hours or high for 3-4 hours, until squash is tender.
Carefully remove the squash from the slow cooker and cut it in half lengthwise. Scoop out the seeds.
Use a fork to scrape the flesh into strands, discarding the skin.
In a serving dish, mix the spaghetti squash with butter, Parmesan cheese, salt, and pepper.
Garnish with chopped parsley.
Serve warm and enjoy your slow cooker spaghetti squash!