Preheat the oven to 325° F. Spray a 9x13-inch baking dish with non-stick cooking spray.
In a 12-inch skillet heat vegetable oil (1 tablespoon). Add onions (1) and red pepper (1) and sauté until they begin to soften about 5 minutes.
Add ground beef (2 pounds) to the vegetables, and cook over medium-high heat, crumbling with the back of a spoon, until there is no longer any pink. Drain excess fat.
Add ¾ cup water and taco seasoning (1 packet) to the beef in the skillet and bring to a boil. Reduce heat and simmer until sauce thickens.
In a small bowl mix together the Bisquick mix (2 ¼ cups) and ⅔ cup water to make a soft dough. Press the dough into the bottom and up the sides about ½ inch in the prepared baking dish. The dough was a little sticky so I used parchment paper to press it out on the bottom, and I used a spatula to bring it up the sides.
In a small bowl mix together the mayonnaise (½ cup), the sour cream (½ cup), and half the cheddar and jack cheeses. Set aside.
Spread the ground beef mixture evenly over the biscuit layer, then top with a layer of the sliced tomatoes (2). Evenly sprinkle the green chilies (1 can) over the tomatoes. Spread an even layer of the the sour cream mixture over the green chilies. Sprinkle top with remaining cheese.
Bake for 30 to 35 minutes or until edges are lightly browned.
Notes
Dough – When you spread the dough into the prepared baking pan, make sure the edges of the dough cover the bottom of the dish.