In a medium bowl, combine flour, cornstarch, Cajun seasoning, garlic powder, salt, baking powder, paprika, peppers, and oregano.
Whisk in beer and egg until smooth. Add catfish. Cover and refrigerate for 1 to 2 hours.
In a deep skillet or large pan, pour vegetable oil to a 3-inch depth. Heat oil to medium-high heat on stovetop.
When oil is hot, lift fish strips with tongs to drain excess batter. Fry catfish in oil, several pieces at a time (being careful not to overcrowd), for approximately 3 minutes per batch, or until well browned on all sides.
Drain on paper towels.
Repeat with remaining catfish, keeping cooked fish warm until ready to serve.