Prep the ingredients – Shred the cheese, dice the onion and mince the garlic.
Preheat the oven to 350 F. Spray a 9x13 casserole dish with cooking spray. Set aside.
Brown the ground beef in a large skillet on medium high heat. Using your spatula, break up the meat into small pieces as it is cooking.
Drain the ground beef. Set aside.
Wipe out the skillet with a paper towel. (Be careful; it will likely still be warm.) Add the olive oil to the skillet and turn it back to medium high heat.
Add in the onion. Stir often. Sauté until onions start to turn translucent.
Turn temperature to medium low. Add the minced garlic and ranch seasoning mix. Stir to combine.
Add ground beef back to pan. Spoon in the cream of mushroom soup and 4 T of milk or water and stir to combine. Remove from heat.
Transfer the beef mixture into the 9x13 baking pan and level it with a spoon or spatula.
Sprinkle 1 ½ cup of cheddar cheese over mixture making sure to evenly coat.
Arrange tater tots in rows across the top of the mixture.
Bake for 30 to 45 minutes or until tater tots start to brown.
Remove the casserole from the oven and sprinkle the remaining cheese on top.
Bake for another 10 minutes or until cheese is fully melted.
Serve while hot!