Preheat oven to 350°F (175°C).
In a skillet, cook ground beef until browned. Drain excess fat. Add taco seasoning and water according to package instructions. Set aside.
In a mixing bowl, combine sour cream, mayonnaise, and half of the shredded cheese. Set aside.
In another bowl, mix Bisquick mix, milk, and eggs until well combined. Pour into a greased baking dish.
Layer the cooked beef mixture over the Bisquick layer in the baking dish.
Spread the sour cream mixture over the beef layer.
Top with diced tomatoes, chopped onions, and bell peppers.
Sprinkle the remaining shredded cheese on top.
Bake in preheated oven for 30 minutes or until the top is golden and bubbly.
Let it cool for a few minutes before serving.