Dates and orange zest add an unexpected twist to this coffee cake-inspired muffin.
Preheat oven to 400 degrees. Line a standard 12-cup muffin tin with baking cups, or lightly brush with butter. In a medium bowl, whisk together oats, flour, baking powder, baking soda, and salt. In another bowl, whisk together buttermilk, butter, brown sugar, orange zest, and eggs. Stir wet ingredients into dry until just combined. Fold in chopped pecans and dates.
In a small bowl, combine oats, flour, brown sugar, and salt. With your hands, work in butter until large, moist clumps form.
Divide batter evenly among muffin cups; top with crumble. Bake until golden and tops spring back when lightly touched, about 20 minutes. Let cool 5 minutes in tin, then transfer to a wire rack and let cool completely.