Preheat a grill or indoor grill pan to medium-high heat (about 375–450°F).
In a small bowl, mix the onion powder, garlic powder, kosher salt, and ground black pepper.
Pat the chicken breasts dry, rub them with the olive oil, then evenly season both sides with the spice mixture.
Brush each chicken breast generously with about 1/2 cup of the Buffalo sauce, coating all sides.
Place the chicken on the preheated grill and cook for 6–8 minutes without moving, then flip and cook another 6–8 minutes until an instant-read thermometer inserted into the thickest part reads 165°F.
After removing from the grill, brush the chicken with the remaining Buffalo sauce and let rest for at least 5 minutes.
Slice the chicken if desired and serve topped with crumbled blue cheese, chopped green onion, and ranch or blue cheese dressing.