Preheat oven to 350 degrees. Spray a 9" x 13" pan with cooking spray. Brown ground beef in a skillet. Drain any grease. Season beef with garlic salt and pepper. Place beef in the baking dish. Place beans and corn on top of beef. In a large bowl, whisk together soup, milk, and sour cream. Spread over ground beef in an even layer. Top with tator tots. Sprinkle tots with seasons salt. Top with cheese. Bake 30 to 40 minutes covered loosely with foil. Uncover and bake another 10 to 15 minutes until cheese is bubbly.