Cook the jumbo pasta shells in a large pot of salted boiling water for about 8-10 minutes, or until al dente. Drain and set aside.
In a large skillet, heat the olive oil over medium heat. Add the minced garlic and ground turkey, cooking until the turkey is browned and cooked through, about 5-7 minutes.
Stir in the chopped spinach and cook until wilted. Remove from heat and let cool slightly.
In a mixing bowl, combine the cooked turkey mixture, ricotta cheese, 1/2 cup of mozzarella cheese, Parmesan cheese, beaten egg, oregano, salt, and pepper. Mix until well combined.
Pour 1 cup of marinara sauce into the bottom of a 9x13 inch baking dish.
Carefully stuff each cooked pasta shell with the turkey and cheese mixture and place them in the baking dish on top of the marinara sauce.
Once all the shells are stuffed, pour the remaining marinara sauce over the top, then sprinkle with the remaining mozzarella cheese.
Cover the dish with aluminum foil and bake in the preheated oven for 25 minutes. Then, remove the foil and bake for an additional 10-15 minutes, or until the cheese is bubbly and slightly golden.
Remove from the oven and let it cool for a few minutes before serving.
Notes
Garnish with fresh basil or parsley for a pop of color. Serve with garlic bread and a simple side salad for a complete meal.