Preheat your oven to 375°F.
Boil the jumbo pasta shells in a large pot of salted water until al dente, then drain and set aside to cool.
In a skillet over medium heat, cook the ground turkey until browned and fully cooked, breaking it into small crumbles.
Finely chop the fresh spinach and squeeze out any excess moisture using a clean kitchen towel.
In a medium mixing bowl, whisk the egg and then stir in the ricotta cheese, chopped spinach, grated parmesan, and half of the garlic powder, oregano, salt, and pepper.
Spread half of the marinara sauce evenly across the bottom of a small baking dish.
Stuff each cooked pasta shell generously with the spinach and ricotta mixture and arrange them in the baking dish.
Top the shells with the cooked ground turkey and the remaining marinara sauce.
Bake for 20 minutes until the sauce is bubbly and the filling is set.