Preheat oven to 375ºF. Using an apple corer or paring knife, core apples to create a 3/4-inch-wide tunnel; do not cut through bottom of apples. Stir together oats, prunes, apricots, 2 Tbsp. maple syrup, cinnamon and cloves. Spoon mixture into apples, packing in filling and mounding it slightly on top.
Place apples in an 8-inch square baking dish and pour 1/2 cup water into bottom of dish. Dot tops of apples with butter and loosely cover with foil. Bake for 20 minutes. Uncover and continue to bake until apples are tender but not falling apart, 20 to 30 minutes longer. Let cool slightly.
Stir together yogurt and remaining 1 Tbsp. maple syrup. Serve with warm apples.