Preheat oven to 400 degrees. Line a baking sheet with parchment and set aside.
Use a spoon to scrape out the tender centers of the zucchini, leaving a ½ inch rim to create a well in each zucchini. Place each zucchini boat on the baking sheet and brush each zucchini with ½ of the oil.
Add remaining ½ tablespoon of olive oil to a medium skillet and place over medium heat. Oncce hot, add in onions and garlic, and saute for 3-4 minutes. Transfer to a large bowl then stir in shredded chicken, BBQ sauce and ¾ cup shredded cheddar cheese; mix well.
Spoon bbq chicken mixture evenly into zucchini boats. Top the zucchini with the shredded cheese.
Bake for 40-45 minutes or until zucchini is tender-crisp. Sprinkle the tops with cilantro and green onion before serving.