Preheat oven to 325° F.
In oven-safe skillet, heat olive oil over medium heat. Add garlic and cook 2 minutes, or until fragrant. Once garlic is fragrant, add spinach; break up to incorporate and heat.
In medium bowl, whisk together eggs, milk, pepper, oregano, ricotta, Parmesan and basil.
Add egg mixture to skillet, reduce heat to low and cook 1 minute, stirring gently. Move to oven and bake 25-30 minutes, or until eggs are almost completely set.
Carefully remove from oven and add mozzarella. Return to oven and bake until mozzarella is melted, about 5 minutes.
May be served hot, at room temperature or cold.