Preheat your oven to 400°F and line a baking sheet with parchment paper for easy cleanup.
Clean the portobello mushrooms with a damp cloth, remove the stems, and carefully scrape out the dark gills using a spoon.
Heat the olive oil in a large skillet over medium heat and add the minced garlic, sautéing until fragrant.
Add the ground turkey to the skillet, seasoning it with sea salt, black pepper, and dried oregano.
Cook the turkey until it is fully browned and cooked through, breaking it into small crumbles with a spatula.
Add the chopped spinach to the skillet and stir until it is just wilted, then remove the pan from the heat.
Allow the turkey mixture to cool slightly before folding in the Greek yogurt until the filling is creamy and well combined.
Place the mushroom caps on the prepared baking sheet and fill each one generously with the turkey and spinach mixture.
Sprinkle the grated parmesan cheese evenly over the top of the stuffed mushrooms.
Bake for 15 to 20 minutes until the mushrooms are tender and the parmesan topping is golden and bubbly.