Preheat your oven to 375°F (190°C) and prepare a baking dish by lightly greasing it with olive oil.

Slice a deep pocket into each chicken breast without cutting all the way through. Pat dry with a paper towel.

Heat a tablespoon of olive oil in a skillet over medium heat, add minced garlic and sauté until fragrant. Add spinach, stirring until wilted.

In a bowl, combine spinach, roasted red peppers, mozzarella, Parmesan, oregano, basil, salt, and pepper. Mix thoroughly.

Fill each chicken breast pocket with the stuffing mixture, securing with toothpicks or kitchen twine.

Sear the stuffed chicken in a hot skillet with olive oil for 2-3 minutes on each side until golden brown.

Transfer to the baking dish and bake for 20-25 minutes until the internal temperature reaches 165°F (74°C).

Let the chicken rest for 5 minutes, then drizzle with balsamic vinegar before serving.