Mix buttermilk and oats in large bowl. Let stand 5 minutes. Whisk in eggs. Mix in flour, sugar, baking soda and salt; stir in chopped hazelnuts. Heat heavy large skillet over medium-high heat. Brush with oil. Drop batter by one third cupfuls into skillet, spacing apart. Cook until bubbles form on top of pancakes, about 2 minutes. Turn and cook until bottoms are golden, about 2 minutes more. Transfer to plate. Repeat with remaining batter, brushing skillet with oil as needed. Serve with maple syrup.