Preheat the oven to 350°F, and line a muffin pan with paper liners.
Combine all of the ingredients in a large bowl. Use a ¼ cup measuring cup to scoop the mixture into your muffin pan, stirring the mixture each time you scoop, so you get all of the goods into each cup.
Bake for 25 minutes. Pull them out of the oven, and let them cool for 10 minutes before serving.
Video
Notes
The oats in the batter are going to want to sink to the bottom of the bowl, which is why you need to stir before each scoop. When you scoop the batter into the muffin pan, make sure you get an even mixture in there. If you don't, your oatmeal cups won't properly set, and you'll be sad. I'd hate that for you!
Don't be shy about filling the cups of your muffin pan all the way up. These aren't muffins, and they won't rise like muffins. Get back in there for another scoop, if you have more batter left after you scoop ¼ cup into each section of the pan.
It's important that you let these cool, so they have time to set. If you pull them out before cooling completely, they will fall apart.
Flavor variation ideas
Blueberry vanilla: omit the orange zest, use 1 cup blueberries instead of cranberries, add 1 teaspoon vanilla extract
Cinnamon apple: omit the orange zest, use 1 cup diced apple instead of cranberries, add 1 teaspoon ground cinnamon
Oatmeal raisin cookiecups: omit the orange zest, use raisins instead of cranberries, add 1 teaspoon vanilla extract, add an optional extra ¼ cup brown sugar
Peaches and cream: omit the orange zest, use 1 cup diced fresh peach instead of cranberries, add 1 teaspoon vanilla extract
Maple walnut: omit the orange zest, increase the maple syrup to ½ cup, add ¾ cup chopped walnuts