Preheat your oven to 375 degrees Fahrenheit (190 degrees Celsius).
In a large oven-safe skillet, add the olive oil over medium-high heat.
Sprinkle the 4 chicken breasts with the taco seasoning on both sides, then sear the chicken in the pan on both sides. The chicken breasts will only need about 2 minutes per side over medium-high heat - the idea is not to cook the chicken through, but just to develop some flavour on the outside of the chicken and in the pan. (Feel free to skip this step to save time - see recipe notes)
In a liquid measuring cup, mix the chicken stock and 1 cup of salsa.
Turn off the heat under the pan. Remove the chicken breasts to a plate and add the chopped bell peppers and rice. Pour the stock mixture over them and mix everything together well.
Add the chicken breasts back in, nestling them into the rice mixture.
Spoon the remaining salsa over top of the chicken breasts. Put the lid on and bake in the preheated oven for 40 minutes at 375 degrees Fahrenheit (190 degrees Celsius). If your skillet doesn't have a lid, you can cover it with aluminum foil.
After the 40 minutes, remove the lid, sprinkle the grated cheese over the chicken breasts, and continue baking uncovered for about 10-15 minutes or until the internal temperature of the chicken is 165 degrees Fahrenheit (74 degrees Celsius). (Because pans and oven temperatures vary, this can affect baking time. Use an instant-read thermometer for best results).
Once the chicken and rice are cooked through, remove the pan from the oven and serve with a sprinkling of fresh cilantro, some sliced jalapeños (optional), and even a dollop of sour cream, if desired.