In a bowl, combine the chopped spinach, crumbled feta, cream cheese, minced garlic, lemon zest, dried oregano, salt, and pepper. Mix until well combined, creating a creamy filling.
Place the chicken breasts between two pieces of plastic wrap. Using a meat mallet or rolling pin, gently pound them until they are about 1/2 inch thick. This will help them roll more easily.
Lay each chicken breast flat and spoon a generous amount of the spinach-feta filling onto each one, spreading it evenly while leaving a small border around the edges.
Carefully roll each chicken breast tightly, starting from one side and rolling it away from you. Secure the ends with toothpicks or tie them with kitchen twine to keep the filling from spilling out.
In a large oven-safe skillet, heat olive oil over medium-high heat. Sear the rolled chicken on each side until golden brown, about 3-4 minutes per side.
Once seared, transfer the skillet to the preheated oven and bake for 20-25 minutes, or until the chicken is cooked through and reaches an internal temperature of 165°F (74°C).
Remove from the oven and let the chicken rest for 5 minutes before removing the toothpicks or twine.
Slice the rolled chicken into medallions to reveal the beautiful filling inside.
Notes
Let the chicken rest before slicing for better presentation.