Dogs are opportunistic. If they find something they want, and they can physically get it, they will. Unfortunately, anything edible on the kitchen counter is usually fair game to a lot of dogs. This is a bad habit for obvious reasons but can also be dangerous because there is the possibility that the dog will one day grab something poisonous (i.e. chocolate) or deadly (cooked chicken bones, ribs, etc) and hurt himself.
First thing, do not set the dog up for failure by placing things near the edge of the counter or leave things open (like uncovered meat or cake). But it sounds like you're doing this already!
Okay, here's what did it for us. It worked like a miracle.
I got a piece of cooked chicken from night before's dinner....basil and garlic, ummm, smelled really good...even heated it in the microwave to get the smell going really well. I rooted through the cabinets and found all the aluminum containers...muffin tins, pie pans, cookie sheets...you want the kind that has a hole at one end. You also want to use aluminum because it is lightweight and makes a good racket when landing on the floor. Then I tied foot-long pieces of string from the chicken piece to each aluminum pan...I used about 5 pans. I placed the chicken about 2" from the edge of the counter, then layed the pans towards the back of the counter. I let Maguire into the kitchen, then went into the TV room and sat down like nothing was going on. This is an important part....if you place a "set up" on the counter and stand in the kitchen, waiting for your dog to take the bait, he will know exactly what is up and won't grab it....a watched pot never boils!!!! A lot of owners try to solve the problem by catching the dog with his paws on the counter, then yelling "OFF!" Well, this works great when you are in the kitchen, but the dog knows when you are sleeping, he knows when you're awake, he knows when you've been bad or good....and gets things off the counter accordingly.
Well, all was quiet for about 5 minutes. Then I hear CRASH!!! and little Maguire feet skittering across the kitchen tile! He took the bait and had not only dropped the chicken but had the bejeebers scared outta him when the pans fell on him and crashed on the floor! Now here's where your reaction is pivotal. You know that high-pitched, cooing, worried-mother voice they tell you *never* to use when a dog is scared, because it only shows him it's okay to be scared? Well, ***use it now!!!*** Crouch on the ground with your arms out, calling the dog in a panicked voice, and when he comes to you, cuddle him and cry and make a big fuss like he just avoided being crushed by a frenzied mob. Lead the dog out of the kitchen and do not let him see you pick up the bait and pans. I must have done a good job with Maguire, because he even threw a leary glance towards the kitchen as I ushered him onto the back porch so I could pick the stuff up.
And, I can honestly say this has worked and he hasn't grabbed anything off the counter since. I think this method works particularly well because the dog associates the correction with the food on the counter, not you....because once the dog knows he only gets corrected when you catch him, he'll be very sneaky about it and even more determined. With this method, you are the "good guy" and the correction came directly from the object the dog was after in the first place.