In a shallow dish, combine the olive oil, garlic powder, chili powder, paprika, cumin, brown sugar, salt, and pepper
Add the chicken breasts to the marinade and turn to coat. Cover and refrigerate for at least 30 minutes.
Preheat the grill to medium-high heat.
Grill the chicken for 4-5 minutes per side, or until cooked through.
In a small bowl, mix together the BBQ and ranch sauces.
Brush the sauce onto the cooked chicken and serve.