Season both sides of the steak with salt and black pepper. Brush with olive oil and let rest at room temperature for 15 minutes.
In a saucepan over medium heat, combine bourbon, brown sugar, soy sauce, Worcestershire sauce, garlic, and red pepper flakes.
Simmer the glaze for 5-7 minutes, stirring occasionally, until thickened. Stir in butter and remove from heat.
Preheat the grill to medium-high heat (about 400°F).
Place steaks on the grill and cook for 3-4 minutes per side, until they develop a nice sear.
During the last 2 minutes of cooking, brush the steaks with the bourbon glaze, flipping once to coat both sides.
Remove the steaks from the grill and let them rest for at least 5 minutes before slicing.
Drizzle with additional glaze before serving for extra flavor.