In a large crockpot, add the olive oil, diced onion, and bell peppers. Stir to combine.
Place the chicken breasts on top of the vegetables. Sprinkle the taco seasoning evenly over the chicken, then pour the salsa over everything.
Add the black beans and corn on top of the salsa. Season with salt and pepper to taste.
Cover the crockpot and cook on low for 6-8 hours or on high for 3-4 hours, until the chicken is cooked through and easily shreds with a fork.
Once cooked, shred the chicken in the crockpot using two forks and mix everything together.
Serve the chicken mixture in tortillas and top with your favorite toppings such as shredded cheese, sour cream, avocado, cilantro, and lime wedges.