Preheat oven to 400 degrees F. Spray a 13 x 9″ baking dish with cooking spray, and set aside.
Heat oil over medium-high heat in a large skillet. Add onion, and saute for about three minutes.
Add ground meat and seasoned salt. Brown and crumble the meat until cooked through.
Stir in frozen vegetables, soup, and sour cream until smooth. Bring to a simmer, and then cook for about 3 minutes. Spread mixture from skillet into prepared baking dish.
Spread cheese over the top of the filling, and then arrange tater tots in a single layer over the cheese. Bake uncovered for approximately 40 minutes or until filling is bubbly and tots are golden brown. Serve warm.