Season the steaks with salt and pepper, and place on the grill. While the steaks cook, heat the oil in large skillet set over medium-high. Add the onion, bell peppers and garlic and cook until tender, about 4 minutes. Add the shrimp, chili flakes, vinegar, salt and pepper and heat the shrimp through, about 2 minutes. Mix in the basil and reserve on low heat.
When cooked to the desired doneness, plate the steaks, top with bell pepper/shrimp mixture and serve.