In a large heavy pot fitted with a deep-fry thermometer over medium-high heat, heat all but 1 tablespoon oil until thermometer registers 375°. Meanwhile, in a small bowl, whisk flour, cornstarch, granulated sugar, baking powder, and salt.
In a large bowl, whisk eggs, milk, and reserved 1 tablespoon oil. Add corn and stir to coat. Fold dry ingredients into corn mixture until just combined.
Working in batches and using a 1 ½-tablespoon cookie scoop, drop heaping scoops of batter into oil. Cook fritters until deep golden brown, 3 to 4 minutes. Using a spider or slotted spoon, transfer fritters to a paper towel-lined plate.
Sprinkle with powdered sugar and serve immediately.
Make Ahead: Fritters can be made 5 days ahead. Store in an airtight container and refrigerate.
