Combine orange juice, taco seasoning, and vegetable oil in a large resealable bag. Add chicken, coat with the marinade, squeeze out excess air, and seal the bag. Marinate in the refrigerator overnight.

Heat a cast iron skillet over medium high heat.

Cook chicken in the hot skillet for 5 minutes. Add onion, green bell pepper, and red bell pepper. Cook until peppers are crisp tender, 4 to 5 minutes. An instant-read thermometer inserted into center of chicken strips should read 165 degrees F (74 degrees C).