In a large sauté pan, heat over medium-high heat. Add the ground beef and cook for about 5-7 minutes, breaking it apart as it browns. Stir occasionally until no pink remains and the meat is fully cooked. Drain any excess grease from the pan.

Once the meat is browned, sprinkle the taco seasoning over the beef and pour in ¼ cup of water. Stir well to combine, then let it simmer for about 4 minutes over medium heat.

Add the chopped onions, Rotel tomatoes, and corn to the seasoned meat. Stir thoroughly and cook for an additional 3-4 minutes until the onions become tender.

In a separate mixing bowl, combine 2 cups of Bisquick with 1 cup of water and stir until you achieve a sticky dough. Grease a 9 x 13-inch baking dish, then spread the Bisquick dough evenly across the bottom.

Carefully spoon the seasoned beef and vegetable mixture over the Bisquick base, spreading it out evenly.

In a bowl, mix together the cream cheese, mayo, garlic powder, and a pinch of salt until smooth and creamy. Spread this mixture over the beef layer with a spatula.

Sprinkle the cheese blend evenly over the creamy topping, ensuring complete coverage.

Preheat your oven to 325°F (160°C) and place the baking dish inside. Bake for 40 minutes, or until the cheese is visibly bubbly and golden brown. Allow the casserole to rest for about 10 minutes once out of the oven.