Preheat your grill to medium-high heat.
In a small bowl, combine the softened butter, minced garlic, sliced pepperoncini, salt, black pepper, and dried oregano. Mix until well combined.
Pat the chicken breasts dry with paper towels and drizzle them with olive oil. Season both sides with salt and pepper.
Place the chicken on the grill and cook for about 6-7 minutes on each side, or until the internal temperature reaches 165°F.
Remove the chicken from the grill and let it rest for 5 minutes.
While the chicken is resting, warm the pepperoncini garlic butter in a small saucepan over low heat until melted.
Serve the grilled chicken topped with the warm pepperoncini garlic butter and garnish with chopped parsley.