Preheat Oven: Heat to 350°F and line baking sheets with parchment.
Mix Wet Ingredients: Whisk marmalade, butter, sugar, baking powder, baking soda, and salt.
Add Dry Ingredients: Stir in flour and oats until no streaks remain.
Portion Cookies: Scoop heaping tablespoons onto sheets.
Bake: Bake 9–13 minutes until edges are golden.
Cool: Cool on wire racks for chewy texture.
