Why does my tempura batter slide off vegetables?

Most often the vegetables are wet. Dry them well and dust with a little flour or starch first, then dip. A very runny batter can also slide off.

Does chilling the coated food help?

A short rest on a rack lets breading set and can help it hold. Follow the recipe if it specifies a rest time.

Crunch and coating · troubleshooting

Why does batter or breading fall off fried food?

Coating falls off when it never bonded to the food in the first place. A wet or slick surface, a skipped binder layer, handling the pieces too much, or flipping before the crust has set are the usual reasons. Dry the food, press the coating on firmly, and leave it alone until it holds.

Likely causes, and how to tell them apart

The surface was wet or slick
What you see: Flour clumped and slid off the food before it ever reached the oil.
The fix: Pat the food dry with towels. For fish, vegetables and tofu, a light dusting of flour first gives the wet layer something to grab.
The layers were not pressed on
What you see: Crumbs sat on top of the egg wash and lifted off in sheets when you picked the piece up.
The fix: Press crumbs firmly onto each side with the flat of your hand, then rest the coated pieces briefly on a rack so the coating can set before frying.
The food was moved too soon
What you see: The coating tore where you poked, flipped or nudged the piece in the first minute.
The fix: Leave pieces alone until the underside has formed a firm crust, then turn once and gently.
The batter was too thin or too thick for the food
What you see: Thin batter ran off the food like water. Very thick batter pulled away as a shell and left a gap.
The fix: Aim for a batter that coats the back of a spoon and drips off slowly. The batters-versus-breadings guide explains which coating suits which food.

Fix it now

If a crust has already started to detach in the oil, do not keep fishing for it. Let the batch finish and strain loose bits out of the oil before the next one so they do not burn.
For the next batch, re-dry the food and press the coating on again.

Next time

Use the dry hand and wet hand method: one hand for the dry dredge, one for the wet layer, so your fingers do not clump the coating.
Hold coated pieces for a few minutes on a rack before frying.
Fry in small batches so the pieces are not bumping each other.

Quick questions

Why does my tempura batter slide off vegetables?: Most often the vegetables are wet. Dry them well and dust with a little flour or starch first, then dip. A very runny batter can also slide off.
Does chilling the coated food help?: A short rest on a rack lets breading set and can help it hold. Follow the recipe if it specifies a rest time.