Preheat your oven to 375°F.
Slice the tops off the bell peppers and remove the internal seeds and membranes.
In a large skillet, heat the olive oil over medium heat and sauté the diced onion and minced garlic until fragrant and translucent.
Add the ground turkey to the skillet, breaking it apart with a spatula, and cook until completely browned.
Stir in the cooked quinoa, tomato puree, sea salt, black pepper, and dried oregano until the mixture is well combined.
Stuff each bell pepper generously with the turkey and quinoa filling.
Place the peppers upright in a baking dish and add two tablespoons of water to the bottom of the dish to create steam.
Cover the dish tightly with foil and bake for 30 minutes.
Remove the foil and bake for an additional 10 minutes until the peppers are tender and the tops are slightly golden.