Preheat the oven to 325°F. Lightly coat a 9x13-inch baking dish with non-stick cooking spray.
Cook the ground beef in a medium saucepan over medium heat until fully browned. Drain the grease, then stir in the taco seasoning and ¾ cup water. Simmer for 3-4 minutes.
Prepare the sour cream mixture by combining sour cream, mayonnaise, half the shredded cheddar cheese, and half the diced onion in a medium mixing bowl. Set aside.
Make the biscuit base by mixing the Bisquick biscuit mix and 1 cup of water in a bowl until a soft dough forms. Press the dough evenly into the bottom and ½ inch up the sides of the prepared baking dish.
Sauté the vegetables. Cook the remaining diced onion and green bell pepper in a skillet over medium heat until slightly tender.
Assemble the layers in the baking dish:
Spread the cooked ground beef evenly over the biscuit base.
Top with the diced tomatoes.
Add the sautéed green bell pepper and onion mixture.
Sprinkle on the diced green chilies.
Spread the sour cream mixture evenly over the top.
Sprinkle the remaining cheddar cheese over the sour cream layer.
Bake in the preheated oven for 30-35 minutes, or until the edges of the biscuit base are golden brown.
Serve and enjoy!
