Preheat oven to 375 degrees F. Slice chicken into thin slices along with peppers and onions. You can use one whole pepper or a half of two different colored peppers for some variety.
In a large skillet add a drizzle of oil over medium heat. Add chicken and season with salt and pepper. Cook until chicken is cooked nearly cooked through, 6-7 minutes.
Add peppers and onions to skillet and continue to cook until they are soft, another 3-4 minutes. Chicken should be cooked through completely at this point. Stir in buffalo sauce and remove from heat.
Add provolone slices to subs in a baking dish. Spoon in the buffalo chicken filling and top with blue cheese.
Bake the subs at 375 degrees F. for 10-12 minutes until toasted and bubbling hot.
Garnish subs with a drizzle of ranch dressing and fresh chives. Serve while warm.