Saute 1/2 onion and 1 red pepper in 1 Tbsp olive oil until desired crispness is achieved (about 5-10 minutes). Move to a bowl and keep warm.
Cut the chicken breasts into strips and rub 2-3 them with the fajita seasoning, and cook in the same skillet. Cook until no longer pink in the middle, about 10 minutes.
Add chicken and sauteed vegetables in a flour tortilla (12") or 2 small(6") tortillas. Top each 12" tortilla with 1/4 cup cheese, 1/4 avocado, and salsa. Enjoy your 30 minute meal! Garnish with salsa if desired.