Preheat the oven to 400°F. Stand the peppers in a baking dish — slice a sliver off any wobbly bottoms so they sit flat.

Heat the olive oil in a large skillet over medium-high. Cook the onion 3 minutes, then the turkey, breaking it up, 5 to 6 minutes until no longer pink. Add the garlic for 30 seconds.

Stir in the quinoa, drained tomatoes, olives, oregano, salt, and pepper. Fold in the spinach until wilted, then half the feta. Taste — the olives and feta bring salt, so adjust at the end.

Pack the filling into the peppers, mounding slightly. Pour a half inch of water into the bottom of the dish.

Cover with foil and bake 30 minutes. Uncover, top with the remaining feta, and bake 10 more minutes, until the peppers are tender.

Rest 5 minutes before serving.