Turn all burners to high, cover and heat grill until hot, about 10 minutes. Turn all burners to high.
Clean and oil cooking grate.
Place potatoes, turning as needed, until tender and browned on both sides, about 5 minutes.
Cook beef until charred on both sides and it registers 130º for medium, 8 minutes.
Bell peppers can be put on at the same time as the potatoes, they will not take more than 5 minutes to become charred and cooked tender, but will have a crunch.
Transfer potatoes and beef to a serving platter, tent loosely with aluminum foil and let rest for 5-10 minutes.
Slide potatoes off skewers, drizzle sauce over potatoes and serve.