Preheat oven to 350 degrees and spray a 7 x 11 inch casserole dish with non-stick spray.
brown the ground beef and onion, drain and transfer to prepared casserole dish.
Stir the taco seasoning, tomato sauce and corn into the ground beef and stir to combine. Spread mixture out to cover the bottom of the dish.
Cover the ground beef with the shredded cheddar cheese
Combine the biscuit mix, milk and eggs until well blended. Pour over the ground beef and cheese to completely cover.
Bake for 40-45 minutes, until the biscuit mix is lightly golden brown.
Remove from oven and let stand for 3-5 minutes, cut into 6 large or 8 smaller squares.
Serve with chopped lettuce, chopped tomato and sour cream