Place chicken breasts in slow cooker along with diced red pepper.
In a small bowl, mix together the ingredients for the buffalo sauce. Set aside a quarter of the sauce.
Pour the remaining sauce over chicken and toss chicken until it’s coated in sauce.
Cook on low for 6-8 hours or on high for 3-4 hours.
Meanwhile, preheat oven to 375 degrees F. Scoop the seeds out of the halved spaghetti squash. Drizzle each half with half a tablespoon of olive oil and sprinkle with salt and pepper. Place each half facedown on a baking sheet or in a large baking dish. Bake for 35-40 minutes.
Once cooked, flip each half over and fluff up spaghetti squash so that you can see strands.
Top each half with buffalo chicken, scooping up sauce from bottom of slow cooker and drizzling over top. This will help flavour up the spaghetti squash. Drizzle with remaining reserved sauce. Top with blue cheese, feta or shredded mozzarella (if desired). Bake for 20 minutes.
To serve, top with diced green onion and additional cheese, if desired.