Your dog is tall enough now. The counter is a shelf holding the best food in the house, and every so often there is something on it. That is enough to keep the habit going for months.
This is not a dog who knows better and does it anyway. This is a dog who has been paid, at unpredictable intervals, for checking.
Why an occasional payoff is so hard to compete with
Your dog checks the counter 30 times in a week, finds nothing 29 times, and the 30th keeps the whole habit alive. Telling them off on check number 12 does not enter into that arithmetic.
Behaviour change here comes from management and reinforcement together. Management removes the payoff. Reinforcement makes the alternative worth doing.
Today, before any training
Clear every counter and table surface, and keep them clear for 2 weeks. Food goes in a cupboard or the fridge, not at the back of the counter.
Bin lid closed, dishwasher shut, cooling cake in the oven with the door shut and the oven off.
Use a baby gate or a closed door while you cook. Cooking is the highest paying 20 minutes of your dog's day, and it is not the moment to test the training.
This is not giving up. A habit that stops paying stops being worth the trip. One successful steal is worth more to your dog than a week of your practice.
Tonight: leaving the counter alone, 8 minutes
Put a plain piece of food on a plate at the back of the counter. Stand 3 feet away with your dog on a leash and 20 better treats in your pocket.
The instant your dog looks away from the plate, say yes and feed 2 treats down by your leg. Do 10 reps.
Slide the plate 6 inches forward each time you get 3 clean looks-away in a row. Finish by walking your dog out of the kitchen, then clear the plate yourself.
You are paying for looking away, not for looking. If your dog cannot take their eyes off the plate, slide it back, add 2 feet of distance, and put duller food on it.
When they already have it
Chasing your dog round the sofa for a stolen bagel teaches them that stealing starts a game. Swap instead: hold 3 treats at their nose, say swap once, and feed them one at a time as your dog lets go.
Where it is safe to, hand the item straight back afterwards, so letting go stops predicting loss. Never pull something out of your dog's mouth.
Safety note
Stop if your dog stiffens, freezes, growls or stands over the item. Speak to your veterinarian or a qualified behaviour professional before you practise swaps again. Taking items from a dog who guards them can escalate to defensive aggression. Call your veterinarian the same day if your dog has swallowed something that could hurt them.
What not to use
Mousetraps, shake cans and remote collars are all sold for this. Aversive methods are associated with worse welfare outcomes and no training advantage. Dogs trained that way showed more stress-related behaviour than dogs trained with rewards. A dog startled at the counter can become wary of the kitchen, of you, or of both.
What to expect
Counters get quieter when the checking stops paying and there is something better to do while you cook. Expect 2 weeks of bare surfaces before you trust the training, and expect one relapse the first time somebody leaves a pizza box out.
Today's version, in one line: clear the counters, then 10 reps with a plate, 8 minutes.