I make this all the time. Good even if it is not the prized recipe.
California Casserole
2 packages frozen California blend
1 1/2 cups prepared rice
1 can mushroom soup
1- 16 oz cheese whiz or any cheese
Thaw vegetables and prepare rice. Mix, add soup and cheese.
Put into a buttered, 9x13 pan. Bake 30 minutes at 350. Last five minutes top with canned onion rings and finish baking.