In a small bowl, stir together the oregano, rosemary, thyme, salt and pepper. Rub the mixture over the chicken thighs.
Heat 1 teaspoon olive oil in a large skillet set over medium-high heat. Add the chicken and cook until browned, about 2 minutes per side. Transfer the chicken to a plate.
Reduce the heat to medium and add the remaining ½ teaspoon olive oil. Add the onion and red bell pepper, and cook until the vegetables are just tender, about 5 minutes. Add the garlic and cook for 30 seconds.
Add the diced tomatoes, balsamic vinegar and chicken broth. Bring to a boil, then nestle the chicken thighs into the tomato mixture. Simmer until the chicken is cooked through, about 10 minutes.