Gather your ingredients.
Preheat a large sautee pan with the extra virgin olive oil; add the chicken breasts and cook until lightly brown, about 10 minutes, season with salt, pepper, oregano and pepper flakes; remove from the heat and set aside.
3 chicken breasts, 1 tbsp oregano, 1 tbsp red pepper flakes, salt and pepper to taste, 3 tbsp extra virgin olive oil
Add the tomato sauce to the pan, bring to a simmer and season with salt, pepper, oregano and pepper flakes; add the chicken breasts and simmer for about 15 minutes.
12 oz tomato sauce, 1 tbsp oregano, 1 tbsp red pepper flakes, salt and pepper to taste
Turn the heat off; top the chicken with the mozzarella slices; cover the pan and allow for the cheese to melt , about 5 minutes; add additional oregano to the top of the melted mozzarella and serve.
6 mozzarella slices