Heat grill to medium heat. Brush the boneless skinless chicken breasts with 1 tbsp vegetable oil, then sprinkle evenly with the pkg Old El Pasoᵀᴹ fajita seasoning mix, coating all sides. In a separate bowl, toss the sliced each large onion with the remaining vegetable oil; set aside so it’s ready to go on the grill later.
Place the seasoned boneless skinless chicken breasts on the grill over medium heat and cook for about 15 minutes, turning occasionally, until cooked through and no longer pink in the center and the internal temp reaches 165°F/71°C. For the last 5 to 7 minutes of the chicken cooking time, add the onion to the grill and cook until crisp-tender.
Slice the grilled boneless skinless chicken breasts and grilled onion. Divide the sliced chicken and vegetables among the pkg Old El Pasoᵀᴹ tortilla bowl (you’ll get about 8 fajita bowls). Add your favorite topping ideas: lettuce; tomatoes; avocadoes; salsa; sour cream; cheese, and serve immediately while piping hot.
