Cut the beef roast into one inch cubes (or 36 pieces of roughly the same size).

In a small bowl combine 1/3 cup balsamic vinegar, 1 Tbsp olive oil, ½ tsp worcestershire sauce, 2 cloves minced garlic, ½ tsp of salt, and some freshly cracked black pepper. Pour the marinade into a zip top bag, add the beef cubes, and marinate for at least an hour.

Lightly wipe off the mushrooms and cut each one in half. Place in a bowl and sprinkle with the remaining 2 Tbsp of balsamic vinegar, 1 Tbsp of olive oil, a pinch of salt, and some more pepper. Toss the mushrooms to coat, and refrigerate until you’re ready to make the kebabs.

Just before you’re ready to make the kebabs, cut the bell pepper and red onion into one inch pieces.

Preheat the broiler on high. Take the meat and mushrooms out of the refrigerator and begin to build your kebabs. If you cut 36 pieces of beef, make sure each kebab has 3 pieces.

Coat a broiler pan with non-stick spray. Place the kebabs on top (6 at a time). Adjust the oven rack so that the top of the broiler pan will be about 4-5 inches from the heat source. Place the kebabs in the oven and broil for 5-7 minutes, turn the kebabs over, and broil for another 5-7 minutes on the second side.

Check your first batch after 3-4 minutes. You will want to flip the kebabs when they have achieved a crispy brown exterior. Use that time as a guide for the rest of your kebabs.