Spread bell peppers and yellow onion onto baking sheet. Top with chicken then sprinkle garlic and seasoning evenly over chicken strips. Drizzle olive oil over top.
Toss everything to coat evenly.
Roast in preheated oven, tossing once, halfway through cooking, until veggies are tender and chicken has cooked through, about 18-25 minutes. Test a few larger pieces to make sure chicken is done, 165 degrees internal temperature. Be sure not to overcook as chicken will be dry.
Wrap tortillas lightly in foil and warm in oven during last 5 minutes of cooking.
Drizzle lime juice evenly over top of the chicken fajita filling, sprinkle with cilantro and more salt to taste, optional, and toss to coat evenly.
Serve filling warm in warm tortillas with desired toppings.