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 bottom of the crockpot. Sprinkle the taco seasoning evenly over the chicken.
Add the sautéed onion and bell pepper mixture on top of the chicken. Pour the salsa, black beans, and corn over everything.
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 directly in the crockpot using two forks and mix everything together.
Serve the chicken mixture in taco shells or tortillas, and top with your favorite toppings.