Preheat oven to 350F. Line a 9×9 baking pan with parchment paper. Set aside.
In a large bowl, combine oats, flour, 3/4 cup sugar, baking powder, cinnamon, nutmeg, and salt. Toss in melted butter, yogurt, and vanilla until mixture is crumbly.
Reserve 2 cups of crumb mixture for topping. Press remaining mixture in prepared baking pan in an even layer.
In a medium bowl, combine cranberries, 1/2 cup remaining sugar, orange juice, marmalade, and cornstarch until evenly coated.
Sprinkle cranberry mixture over crust and top with reserved crumb mixture. Bake bars at 350F 45-50 minutes until topping is golden-brown and filling is bubbly. Allow bars to cool completely on a wire cooling rack.