Preheat oven to 375°F.
Wash and dry zucchini thoroughly.
Cut each zucchini in half lengthwise.
Scoop out flesh with spoon carefully.
Brush zucchini boats with olive oil.
Season with salt and pepper.
Heat skillet over medium heat.
Cook ground turkey until browned.
Add onion and garlic to pan.
Cook until onion becomes translucent.
Stir in marinara sauce and herbs.
Fill zucchini boats with meat mixture.
Top with mozzarella cheese generously.
Sprinkle breadcrumbs over cheese layer.
Cover with foil and bake.
Bake for 25-30 minutes total.
Remove foil last 5 minutes.
Let cool before serving.