Remove the steaks from the refrigerator and place them on the counter 30 minutes beforehand to allow them to come to room temperature.
In a small bowl, whisk together the olive oil, salt, pepper, and garlic powder. Set aside.
Pat the steaks dry with a paper towel, then brush the oil mixture evenly over both sides of the steaks.
Preheat the grill to 450 - 500 degrees F and grease the grill grates.
Place the sirloin steaks on the hot grill and sear one side for 3-5 minutes, then flip them over and sear the other side for the same amount of time.
Start testing the steaks by inserting an instant-read thermometer into the thickest part of the meat. It is ready when the meat reaches an internal temperature of 130 degrees F (medium-rare). If they are not quite ready, continue cooking and flipping the steaks for 2 minutes on each side until they are cooked to medium-rare.
Remove the steaks from the grill and place them on a cutting board.
Let the meat rest for 8 minutes (to keep the juices locked in) before slicing.
Thinly slice the steaks across the grain and serve.