Place the chicken breasts, chicken broth, onion quarters, and minced garlic into a large skillet or pot.
Sprinkle the chili powder, cumin, oregano, salt, and pepper over the chicken.
Bring the liquid to a simmer over medium-high heat.
Reduce the heat to low, cover the skillet, and cook for 15 to 20 minutes, or until the chicken is cooked through (internal temperature reaches 165°F).
Remove the chicken from the skillet and place it on a cutting board. Reserve the cooking liquid.
Use two forks to shred the chicken completely.
Return the shredded chicken to the skillet with the cooking liquid. Stir to coat the chicken thoroughly. Cook uncovered for 2 to 3 minutes until the liquid reduces slightly and the chicken is moist.
Warm the tortillas according to package directions (stovetop or microwave).
Fill each tortilla with the shredded chicken mixture. Serve immediately with your desired toppings.
Notes
For extra flavor, add 1 teaspoon of smoked paprika to the seasoning mix.
If you prefer a spicier taco, add 1/4 teaspoon of cayenne pepper with the other spices.
You can use the leftover shredded chicken filling for bowls or nachos later in the week.