Preheat oven to 350°F.
Slice both ends from squash and discard. Stand squash up on one of it's cut ends and use a large knife to cut the squash in half lengthwise. Scoop seeds and stringy insides out using a large spoon.
Place squash cut-side down on the baking sheet.
Bake for 30-40 minutes or until squash is tender.
When squash is tender, allow to cool slightly before using a fork to gently scrape the squash into a large bowl. Reserve the squash shells.
While squash is roasting, cook the chicken in medium pan over medium-high heat. Add 1 tsp. avocado or coconut oil and swirl pan to coat with the oil. Add chicken and ½ cup water. Once the water begins to simmer, reduce heat and cover. Cook chicken for 15-18 minutes or until cooked through. Move chicken to a cutting board to cool slightly before shredding with two forks.
Place squash shreds, chicken, celery, onions, peppers and Buffalo sauce in a large bowl. Toss well to coat. Spoon squash mixture into the squash shells. Return the stuffed shells back to the baking sheet and place in 350°F oven for 10-15 minutes or until heated through.