Step 1) Combine oil, bourbon, Worcestershire sauce, brown sugar, garlic, salt and pepper in a 1-gallon plastic freezer bag. Add beef, mushrooms and red bell pepper, turning to coat. Refrigerate and marinate for at least 30 minutes.
Step 2) Remove beef and vegetables from marinade; discard marinade. Thread onto four 12-inch skewers or eight 8-inch skewers.
Step 3) Grill over medium high heat, turning once, about 3 to 4 minutes on each side, until vegetables have char marks and steak is cooked to the desired degree of doneness.
Recipe Note: If using bamboo skewers, make sure to soak the skewers in water for 30 minutes before using.