Preheat: Preheat the oven to 350°F and spray a 9X13-inch casserole dish with nonstick cooking spray.
nonstick cooking spray
Prep: Chop the onion and bell pepper and grate the cheese.
Make the topping: Combine the mayo, sour cream, and 1 cup of the cheese in a small bowl. Set aside.
½ cup sour cream, ½ cup mayonnaise, 1 cup shredded cheddar cheese
Cook the beef: Cook the ground beef, onion, and bell pepper in a large skillet over medium-high heat, stirring occasionally, until the beef is browned. Drain if not using lean ground beef. Add the taco seasoning and tomatoes and cook, stirring constantly, until combined and heated through.
2 pounds lean ground beef, 1 cup onion, 1 green bell pepper, 1 can diced tomatoes with green chiles, 2 packets taco seasoning
Make the biscuit base: In a medium bowl, combine the biscuit mix and milk, mixing just until combined. Press evenly into the bottom of the prepared casserole dish.
2 ¼ cups biscuit mix, 1 cup milk
Assemble the casserole: Spread the beef mixture over the biscuit base, then top with the sour cream mixture and 1 cup shredded cheddar cheese.
1 cup shredded cheddar cheese
Bake: Bake for 30–35 minutes, or until hot and bubbly.