Preheat a grill or indoor grill pan to medium-high (about 375–450°F).
In a small bowl, combine the onion powder, garlic powder, kosher salt, and ground black pepper.
Rub the chicken breasts with the olive oil, then evenly coat them with the spice mixture.
Generously brush the chicken on all sides with about 1/2 cup of the Buffalo sauce.
Place the chicken breasts on the preheated grill and cook for 6–8 minutes.
Flip the chicken and continue grilling another 6–8 minutes, until the internal temperature reaches 165°F and the chicken is cooked through.
After removing from the grill, brush the chicken with the remaining Buffalo sauce.
Let the chicken rest at least 5 minutes, then slice and serve topped with crumbled blue cheese, chopped green onion, and ranch or blue cheese dressing.