To make your One Pan Balsamic Chicken, follow these straightforward steps:

1. Preheat the Oven: Start by preheating your oven to 400°F (200°C).
2. Marinate the Chicken: In a mixing bowl, combine balsamic vinegar, olive oil, minced garlic, oregano, thyme, salt, and pepper. Place the chicken breasts in the marinade, ensuring they are well coated. Let them marinate for at least 15 minutes (or up to 2 hours if you have more time).
3. Prepare the Pan: Take a large oven-safe skillet and place it over medium heat. Add a drizzle of olive oil if necessary.
4. Sear the Chicken: Once the pan is hot, carefully add the marinated chicken. Sear for about 5 minutes on each side until golden brown.
5. Add the Vegetables: Next, add the sliced bell peppers and red onion to the pan surrounding the chicken.
6. Pour Remaining Marinade: Drizzle the remaining marinade over the chicken and vegetables, ensuring even coverage.
7. Bake: Transfer the skillet to the preheated oven and bake for 25-30 minutes until the chicken is cooked through and reaches an internal temperature of 165°F (75°C).
8. Add Spinach: In the last 5 minutes of cooking, add the spinach to the pan, giving it time to wilt.
9. Garnish: Once out of the oven, let the dish rest for a few minutes. Garnish with fresh basil leaves before serving.

Following these steps guarantees a deliciously aromatic meal that will impress everyone at the table.