Preheat oven to 350F. Slice a small wafer from the bottom of each pepper to help it stand upright without wobbling. Use a sharp knife to slice away the top of the bell peppers to create a cup. Cut away the seeds from the cap and stem of the pepper and reserve the cap to perch on top of the stuffed peppers. Arrange the hollowed peppers in a baking pan. Bake for 15 minutes uncovered.
While the peppers are baking, place a large, heavy bottom skillet over medium-high heat. Pour 1 tablespoon of the olive oil in and swirl the pan to coat. Crumble the ground turkey over the pan and sprinkle in the salt and pepper. Cook and break up with a sturdy spoon or spatula until the meat is nicely browned and has given off its juices, about 8 to10 minutes. Transfer the cooked meat to a rimmed plate or bowl. Tent lightly with foil and set aside.
Return the pan to the burner immediately. Add another tablespoon of olive oil to the pan. Reduce the heat under the pan to medium-low heat and stir in the grated onion and juices. Cook for 3 to 5 minutes, or until the onions have softened.
Raise the heat to medium-high and stir in the garlic, oregano and thyme cooking until fragrant, about 30 seconds. Stirring constantly, whisk in the tomato paste and cook until the paste is bubbly, has darkened and smells strongly of tomato. Pour in the red wine and raise the heat to high, scraping and stirring until the mixture is smooth and somewhat reduced. Return the browned meat and any accumulated pan juices to the pan and toss until evenly distributed and hot through. Add the baby spinach to the pan and toss to combine with the turkey and sauces. Cook only until the spinach is wilted.
Transfer the turkey mixture to a large mixing bowl. Add the cooked rice and feta to the bowl and toss to distribute all of the ingredients evenly. Divide the filling between the partially cooked peppers, gently packing the filling into them. Place a pepper cap on each stuffed pepper. Add 3 tablespoons of water to the pan and cover tightly with foil. Return the pan to the oven and bake for 10 minutes. Remove the foil and bake 15 minutes longer, or until the peppers are tender.