Preheat oven to 375 degrees. Cover a baking sheet with foil.
Halve spaghetti squash around the “equator,” forming 2 short halves. (This helps keep the long strands intact.) Scrape out the seeds. Coat the cut ends with a little olive oil and place those on the baking sheet. Bake until tender, 35 – 45 minutes.
While the squash is cooking, saute bacon over medium heat to desired level of crispy. Remove and drain on paper towels.
Drain most of the grease, leaving a couple of tablespoons. Turn heat down to medium low. Add onions, garlic, and oregano. Saute, stirring occasionally, until soft and beginning to brown, about 10 minutes.
When squash is done, allow to cool for 10 minutes. Using a fork, scrape the strands out into a bowl. Toss with onions and bacon; season with salt and pepper to taste.