Cut the sirloin steak into cubes (about 1 to 1.5 inches across). Stir together bourbon, 1 tbsp olive oil, rub and salt, then pour over steak cubes and toss to coat. Marinate in the refrigerator for at least an hour, up to overnight.

In the meantime, cut onion and bell peppers into chunks and toss with remaining olive oil and salt and pepper.

Preheat grill to about 450° while you assemble the kabobs. To assemble, place one piece of meat on the skewer, followed by pepper and onion chunks and repeat 3-4 times. You should have enough ingredients to fill about 4-6 skewers, depending on how much you put on each one.

Place the skewers on the grill and cook for about 4 minutes, keeping the grill temperature between 450 and 500°. Flip and cook for another 4 minutes. This grilling time will result in medium to medium-well steak. There will be some variation between steak pieces since the size of the pieces will not be exactly uniform.

Remove from grill and allow kabobs to rest for 3 minutes before serving. Leftovers can be stored in the refrigerator for up to a week.