Preheat your oven to 325°F (165°C) and lightly grease a 9×13-inch baking dish.
In a large skillet over medium-high heat, cook the ground beef until fully browned, breaking it apart as it cooks. Drain any excess grease.
Stir in the taco seasoning and ¾ cup water. Simmer for 3–4 minutes until slightly thickened. Remove from heat.
In a medium bowl, combine the sour cream, mayonnaise, ½ cup of the shredded cheddar cheese, and half of the diced onion. Mix well and set aside.
In another bowl, mix the Bisquick and 1 cup water until a soft dough forms.
Press the dough evenly into the prepared baking dish, covering the bottom and slightly up the sides (about ½ inch).
Return the skillet to the heat and add the remaining onion and diced bell pepper. Sauté for 3–4 minutes until slightly softened.
Layer the cooked ground beef evenly over the biscuit base.
Add the diced tomatoes, sautéed peppers and onions, and green chiles over the beef layer.
Spread the sour cream mixture evenly over the top.
Sprinkle the remaining cheddar cheese over everything.
Bake for 30–35 minutes, or until the edges are golden and the casserole is set.
Remove from the oven and let it rest for 5–10 minutes before slicing.
Serve warm, optionally topped with sour cream or salsa.
Enjoy!
