Preheat oven to 400 degrees. Line a large, rimmed sheet pan with parchment.
In a medium bowl, combine the ricotta, parmesan, 2 teaspoons oregano, lemon juice, basil, lemon pepper, and salt.
Place the chicken breast on the prepared pan.
Cut a slit into the chicken to create a pocket. Repeat with all the chicken.
Divide the ricotta mixture between the chicken breasts, and fasten with toothpicks to close.
Ladle spaghetti sauce over the chicken breasts, dividing evenly. Divide mozzarella between chicken.
Bake for 30-35 minutes, or until a meat thermometer registers 165 degrees in the thickest part of the chicken.
Sprinkle with remaining oregano prior to serving.