We like doing roasted kernel corn on the grill. We use frozen corn (4 bags containing 5 servings). Season with a rub of your choice to taste, add a stick of butter to the aluminum half pan, chop up some garlic real fine, and cook till the kernels start to get a little roasty. For presentation, use full lettuce leaves to create a 'bowl' to scoop the corn in. In veggies and beans, the judges usually have utensils to use - but I'd find out first.
You can also do grilled corn on the cobb with the same seasoning, garlic, and butter. Just melt the butter and make a slather, then apply regularly while grilling, and to finish.
Good luck.