Heat oil in a deep-fryer or large saucepan to 375 degrees F (190 degrees C).
Preheat the oven to 200 degrees F (95 degrees C).
Whisk flour, beer, black pepper, and salt together in a bowl to make batter. Submerge cauliflower pieces in batter to coat. Working in batches of 10, drag 1 piece at a time gently against the rim of the bowl to remove excess batter and transfer to the hot oil. Fry cauliflower, stirring gently to keep pieces separate, until golden, 2 to 4 minutes.
Use a slotted spoon to transfer fried cauliflower to a baking sheet lined with paper towels. Keep warm in the oven.
Return oil to 375 degrees F (190 degrees C) between batches and continue frying cauliflower.