I like giving veggies to my dogs and of course make sure they are cooked so James can digest them. Some favorites are broccoli, cauliflower, green beans, carrots, squash, sweet potatoes. Some dogs love raw carrots but these are more of a treat as they can't pull the nutrients out of them as if they are cooked. My current dogs don't like raw carrots. Fruit is also good, peeled and cored apples, peaches, bananas, stawberries.
I never feed tomatoes, onions, peppers, corn, and some dogs don't do well on potatoes. With the fruit I never feed grapes / raisins.