Preheat the oven to 375 degrees F
Slice the red onion, and bell pepper into strips. Place all of the vegetables onto your sheet pan. Mix with your olive oil and taco/fajita seasoning mix.
Place the sheet pan on the middle rack and roast for about 15-20 minutes. Once the vegetables have started to caramelize a little bit (brown slightly on the outsides), add the shredded chicken and black beans, mix into the mixture. Cook for another 5-10 minutes to thoroughly heat the chicken and beans.
Remove from the oven and let cool. Heat your tortillas and gather all your accoutrements - sour cream, avocado, salsa, cilantro, etc. Heat those tortillas and enjoy!