In a medium bowl, whisk together olive oil, tamari soy sauce, lemon juice, aged red wine vinegar, Worcestershire sauce (if using), honey, Dijon mustard, garlic (both fresh and powder, if you choose), smoked paprika, and thyme leaves. This mélange of ingredients creates a robust marinade that will infuse the steak with flavor.

Cut the sirloin steak into 1-inch cubes. Place them into a resealable plastic bag or a glass dish and pour the marinade over the beef. Seal or cover and refrigerate for at least 30 minutes, but ideally, allow it to marinate for 2-4 hours. If you really want the flavors to deepen, let it marinate overnight.

While the steak marinates, chop your vegetables. Cut the bell peppers into bite-sized pieces, slice the red onions, and clean the cremini mushrooms. Don’t forget to mince some fresh garlic to add more flavor!

Once the steak has marinated, it’s time to skewer! Alternate threading the steak and vegetables onto the skewers. Make them colorful for a feast for your eyes as well as your stomach.

Preheat your grill over medium-high heat. Make sure the grates are clean. Lightly oil them to prevent the kebabs from sticking.

Place the skewers on the grill, ensuring they don’t touch each other. Grill for about 8-10 minutes, turning every few minutes. Cook until the steak reaches your desired doneness; about medium-rare is recommended for optimal tenderness.

When the kebabs are done, remove them from the grill and let them rest for a few minutes. Serve them hot with your choice of sides.