Preheat the oven to 350 degrees F. Lightly coat a 2-quart baking dish with cooking spray.
Heat the olive oil in a large nonstick skillet set over medium-high heat. Add the onion and ground turkey. Cook, breaking up the turkey with a wooden spoon, until the turkey is cooked through, about 5 minutes.
Stir in the garlic, oregano, red pepper flakes, salt and pepper, and cook for 1 minute.
Add the crushed tomatoes, bring to a boil, then simmer for 10 minutes.
Stir in the cooked rice, ¼ cup of the feta cheese and the parsley. Transfer the mixture to the prepared baking dish and top with the remaining feta cheese.