In a large skillet, heat the olive oil over medium heat. Add the diced onion and bell peppers, cooking until softened, about 5 minutes. Season with salt and pepper.
Place the chicken breasts in the crockpot. Sprinkle the taco seasoning over the chicken, then pour the salsa on top.
Add the cooked onion and bell pepper mixture, black beans, and corn to the crockpot. Stir gently to combine.
Cover and cook on low for 6-8 hours or on high for 3-4 hours, until the chicken is cooked through and shreds easily with a fork.
Once cooked, shred the chicken in the crockpot using two forks and stir to mix with the other ingredients.
Serve the chicken mixture in taco shells or tortillas and top with your favorite toppings.