Preheat the oven to 375F. Line a baking sheet with parchment paper.
Cut bell peppers in half lengthwise. Discard the stem and scoop out the seeds and membranes.
Put bell pepper halves on microwave-safe plate and microwave on High for 5 minutes, or until tender.
Heat olive oil in a large non-stick frying pan over medium-high heat. Add ground turkey and cook, stirring occasionally, for 5 minutes, or until cooked through. Add tomato sauce, salt, pepper and 1 1/2 cup shredded cheese and mix until combined.
Put bell pepper halves on a baking sheet. Put the meat mixture inside the peppers. Sprinkle the remaining shredded cheese on top.
Put stuffed bell pepper halves in the oven and bake for 15 minutes, or until the cheese is melted.