Preheat your oven to 375°F (190°C).
Prepare the stuffing by mixing ricotta, mozzarella, spinach, sun-dried tomatoes, garlic, oregano, salt, and pepper in a bowl.
Make a pocket in each chicken breast using a sharp knife, being careful not to cut all the way through.
Stuff each chicken breast with the filling, pressing gently to secure it inside. Use toothpicks to seal the openings if necessary.
Drizzle olive oil over the stuffed chicken and sprinkle breadcrumbs on top for added texture.
Place the stuffed chicken breasts in a greased baking dish and bake for about 25-30 minutes, or until the internal temperature reaches 165°F (75°C).
Allow the chicken to rest for 5 minutes before serving.
Serve warm and enjoy your homemade Ruth's Chris Stuffed Chicken!