Place tenderloin, 1 Tbsp olive oil, balsamic vinegar, BBQ sauce, vinegar and garlic in a resealable plastic bag. Mix well to distribute marinade over tenderloin. Place in refrigerator at least 30 minutes to marinate.
Place bell pepper, onion and mushrooms in a large bowl with remaining 1 tsp. olive oil. Mix well and sprinkle with salt and pepper as desired.
Grill or roast tenderloin until fully cooked. Grill or roast veggies until crisp tender.
Serve on lettuce leaves and allow guests to add extra toppings as desired.