Preheat oven to 350°F (175°C). Grease a 9x13-inch baking dish thoroughly.

Mix the Bisquick and water in a bowl until a soft dough forms. Spray your fingers or a spatula lightly with non-stick cooking spray. Press the dough evenly into the bottom of the prepared baking dish. Optional: Pre-bake the crust alone for 5 to 8 minutes to firm the surface before adding toppings.

In a large skillet over medium-high heat, brown the ground beef with the diced onion and red bell pepper until the meat is fully cooked and the vegetables are softened, about 8 to 10 minutes. Drain excess grease thoroughly.

Stir the taco seasoning and 1/4 cup water into the beef. Simmer for 2 to 3 minutes until the sauce thickens and coats the meat evenly.

Spread the seasoned beef mixture evenly over the biscuit dough. Scatter the drained Rotel tomatoes over the beef layer and spread to the edges.

In a medium bowl, whisk together the sour cream, mayonnaise, garlic powder, 1 cup of shredded cheddar, and drained green chiles until smooth. Spread evenly over the Rotel layer using the back of a spoon, working to the edges without pressing down into the layers below.

Sprinkle a generous handful of extra shredded cheddar over the entire surface.

Bake uncovered for 30 to 35 minutes until the cheese topping is bubbling across the surface and golden at the edges, and a toothpick inserted into the corner biscuit base comes out without raw dough.

Remove from the oven and rest for 10 minutes before cutting. Use a flat metal spatula for clean, intact servings.