In a large bowl, whisk together the Fancy Peasant Extra Virgin Olive Oil, Aged Balsamic Vinegar, lemon juice and zest, garlic, Mountain Oregano Salt, and a few cracks of black pepper. Add the beef tenderloin tips and toss until evenly coated. Let marinate for 1 hour at room temperature, or cover and refrigerate overnight for deeper flavor.
Preheat your grill to 400°F. If using wooden skewers, soak them in water for at least 30 minutes. Thread the marinated beef onto skewers, alternating with onion wedges and mushrooms.
Grill over direct heat, turning occasionally, until the beef reaches your preferred level of doneness and the vegetables are lightly charred, about 8–12 minutes.
Transfer the skewers to a platter and let rest for a few minutes. Finish with a sprinkle of Mountain Oregano Salt, serve warm, and enjoy.