Preheat the oven to 350 degrees F. Grease a baking dish with oil and set it aside.
Prepare the sauce: Heat a large skillet over medium heat. Add the butter and garlic, and sauté for a minute. Stir in the heavy cream, and once it starts to boil, add oregano, salt, and pepper. Let it simmer for 2-3 minutes. Add Parmesan cheese and stir until melted. Remove the sauce from heat and set it aside.
In a medium bowl, combine spinach, artichoke hearts, and pesto. Mix well and set aside.
To the prepared baking dish, add ½ cup of the prepared sauce and spread it evenly. Add half of the artichoke pesto mixture over the sauce. Arrange the ravioli over it in a single layer.
Spread another layer of sauce over the ravioli, followed by the remaining artichoke pesto mixture. Arrange the remaining ravioli and finish with spreading the remaining sauce. Sprinkle mozzarella cheese on top.
Cover with foil wrap and then bake the ravioli for 30 minutes until the cheese has melted and the dish is heated through. The uncover and bake for another 30 minutes until the cheese looks golden brown.
Garnish with parsley before serving.