Preheat your air fryer to 375°F (190°C). *If your air fryer doesn't have a preheat setting, just turn it on about 10 minutes before you add the potatoes.
While the air fryer preheats, Set the red potatoes on a cutting board and use a sharp knife to cut them into bite-sized pieces, about 1/2-inch.
Add the diced potatoes to a large colander and place it in the sink under cold running water for about 2 minutes, turning them a few times.
Lay the potatoes out on a few sheets of paper toweling and use a few more paper towels to pat them dry.
Transfer to a large bowl. Add oil and seasonings, and stir with a spoon or toss gently with your hands to coat.
Arrange the potatoes in the the hot air fryer basket, being careful not to overcrowd it. Air fry for 20 minutes, shaking the basket or using tongs to turn them over after 10 minutes. Near the end of the cook time, watch them closely to prevent them from burning.
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Notes
Don't overcrowd the air fryer basket. It's better to cook in batches so the potatoes cook evenly and crisp up nicely.
Refrigerate leftovers in an airtight container for up to 4 days, per USDA.
Reheat the cooked red potatoes in the air fryer or on a sheet pan in the oven at 350°F. until heated through.