Set oven to 375 degrees and prepare a baking pan.
In a bowl mix the garlic powder, chicken stock, wheat free tamari, balsamic vinegar, and olive oil. Pour the sauce over the peppers and onions in another large bowl.
Split the chicken breats and put into baking pan.
Pour the sauce over chicken and put vegtables on top. Cover with foil.
Bake in middle of oven for 40 minutes. Baste the chicken with the sauce at halfway point.