In the meantime, heat the oil in a non-stick pan over medium heat. Add the sausage and sauté breaking it up into smaller pieces until it is no longer pink. Add the garlic and sauté for 3 minutes, then add spinach and cook until wilted. Season with salt and pepper, then set aside to cool.
Combine the eggs, ricotta, oregano, and parmesan in a bowl, season with salt and pepper, and pour into the pie crust. Top with tomatoes, sausage spinach mixture, and feta.
Bake in the oven until a toothpick inserted into the center comes out clean (about 35 minutes). Remove from the heat. Let stand for 5-10 minutes before cutting into wedges and serving warm.