Whisk flour, oats, pecans, baking powder, baking soda, cinnamon, and salt in a large bowl. Whisk egg, buttermilk, 2 Tbsp. maple syrup, and 2 Tbsp. oil in a medium bowl; mix into dry ingredients.
Heat a griddle or large nonstick skillet over medium; brush with oil. Place 2 apple slices in skillet, spacing about ?? apart, and cook until lightly golden, about 1 minute. Turn over and pour ? cup batter over apples, spreading batter to cover. Cook pancake until bottom is golden brown and bubbles form on the surface, about 3 minutes. Flip and cook until cooked through and another side is golden brown, about 2 minutes. Transfer to a plate. Repeat with remaining apple slices and batter, brushing griddle with more oil as needed.
Serve pancakes with yogurt and maple syrup drizzled on top.
