Preheat the oven 350 degrees F. Generously grease or spray a 9 x 13 inch baking dish. Place biscuits in the pan and press them out lightly so they cover the bottom. Place the baking pan on one or two sheet pans to insulate the bottom. Bake the biscuit layer for about 15 minutes.
Add a teaspoon of oil (or use cooking spray) to a large skillet. Brown ground beef over medium heat. When cooked and no longer pink, drain off any excess fat then add the water, taco seasoning mix, and can of Rotel. Stir to combine well. Then add ground beef mixture to the top of the baked biscuit layer. Set aside.
Add 2 teaspoons of oil to the same pan. Add the sliced onions and bell peppers to the pan. Season with salt and pepper to taste. Cook until softened and slightly golden brown around the edges. Add the garlic and cook one minute more. Remove from heat and to the top of the meat mixture.
Mix mayo, sour cream, and sharp cheddar cheese together in a medium bowl. Spread sour cream mixture over the peppers and onions. Spread evenly all the way to the edges of the casserole dish.
Bake for 20 to 30 minutes, or until the top is melted and edges are lightly browned. I continue to bake on two sheet pans so the bottom of the biscuits don't get overdone.
Top with sliced green onions or chopped parsley or cilantro if desired.
