Preheat oven to 400 degrees. Cut squash in half lengthwise, scoop out the seeds with a spoon and discard.
Place squash cut side down on baking sheet and drizzle flesh with olive oil. Roast squash until tender, about 30 to 45 minutes depending on the size.
Once cool enough to handle, use a fork to scrape out strings and transfer a large bowl.
Next, add chicken, BBQ sauce, eggs to the squash and mix together until combined.
Add mixture to a baking dish, top with sliced onions and cilantro, and bake for 30 minutes.