Preheat the oven to 350°F/180°C, and spray a 9x13 inch casserole dish with non stick cooking spray.
Press the biscuits into the bottom of pan so they overlap and cover the entire surface. Bake for 15 minutes.
In a skillet, heat 1 tablespoon of olive oil and cook and crumble the ground beef until browned. Drain away the fat, then season with taco seasoning. Add salt if needed, then add water and cook for 3-4 minutes, stirring to combine. Add the ROTEL tomatoes and cook until the mixture is just warmed through, then pour the meat over the cooked biscuit layer.
Add the ROTEL tomatoes and the corn to the meat and cook until the mixture is just warmed through, then pour the meat over the cooked biscuit layer.
Wipe the skillet clean, heat the remaining oil and saute the onion and peppers for about 2 minutes until they are cooked but still firm. Season with a pinch of salt. Layer the vegetables over the ground beef in the casserole dish.
To make the topping, combine the mayonnaise, sour cream, onion powder and half of both the cheddar and mozzarella cheeses in a bowl. Layer this over the vegetables, then sprinkle the remaining cheeses on top.
Bake for 20-30 minutes, or until the cheeses are melted and starting to brown. Remove from the oven, and garnish with fresh parsley before serving.
You can buy ROTEL in mild, original, or hot varieties. Choose your spice level. If you want the casserole extra mild, use plain diced tomatoes instead.
You do not need to add salt to the meat mixture if the taco seasoning you use has salt in it. Most taco seasoning packets have plenty of salt in them already.
You can use Mexican blend shredded cheese in place of the mozzarella and cheddar if you prefer.
Feel free to leave out the corn if you like.
To Store: Store leftover casserole in an airtight container in the fridge. It will stay fresh for 3-4 days and can be easily reheated in the microwave or oven.
To Freeze: transfer leftovers to a freezer container and store in the freezer for up to 3 months. Defrost overnight in the refrigerator before reheating.