Heat grill pan over medium-high heat or heat outdoor grill. Heat oven to 300˚F.
Combine tomatoes, jalapeño or Serrano peppers, onions, cilantro, salt and 1 teaspoon of lime zest and the juice of 1 lime.
Coat corn and fish with liberal drizzle of vegetable oil to keep it from sticking to grill. Season the corn and fish with salt and pepper. Season the fish with Old Bay. Cook corn 12-15 minutes until kernels begin to darken in spots. Remove corn and cool to handle, then scrape corn from the cob. Grill fish 8-10 minutes until cooked through and firm. Place fish in bowl and flake the flesh with a fork.