Heat gas or charcoal grill to medium heat. Pat the flank steak dry, then sprinkle it generously on both sides with the pkg Old El Pasoᵀᴹ fajita seasoning mix, pressing the seasoning into the steak so it adheres well.

Place the seasoned flank steak on the direct heat of the grill over medium heat. Arrange the small onion, red bell pepper and green bell pepper on the indirect heat side of the grill. Cover the grill and cook 12 to 14 minutes for medium doneness, turning the steak and vegetables as needed so they cook evenly. The steak should be cooked through to your desired doneness and the vegetables should be tender and lightly charred. Remove the steak and vegetables from the grill; let the steak rest 10 minutes so the juices redistribute. After resting, cut the flank steak into slices diagonally across the grain, and cut the grilled red bell pepper and green bell pepper into slices for serving.

To assemble, spoon the sliced grilled steak, grilled small onion, and sliced red and green bell peppers into the pkg Old El Pasoᵀᴹ tortilla bowls. Top each tortilla bowl with fresh toppings ideas: diced avocado, or your desired toppings, and serve immediately while everything is hot.