Preheat your oven to 350°F (175°C). Lightly grease a 9x9-inch or similar baking dish.
In a large mixing bowl, combine the drained corn, fiesta corn, green chiles, cream cheese, sour cream, ¾ cup of the cheddar cheese, garlic powder, chili powder, salt, and pepper. Mix until everything is evenly coated and creamy.
Spread the mixture into the prepared baking dish. Top with the remaining ¼ cup of cheddar cheese. Add crushed tortilla chips or jalapeños if using.
Bake uncovered for 25–30 minutes, or until hot, bubbly, and slightly golden on top.
Remove from the oven and let cool for a few minutes. Garnish with chopped cilantro or green onions if desired. Serve warm.