Mix Together The Cream Of Chicken Soup And Beef Gravy In A Slow Cooker, Cover, And Set The Cooker To Low. With A Meat Tenderizing Mallet Or The Edge Of A Small, Sturdy Plate, Pound The Beef Round Steaks On A Work Surface Across The Grain Of The Meat To Make Many Small Cuts Across The Meat Fibers. Sprinkle Greek Seasoning On Both Sides Of The Steaks, And Sprinkle Dry Chicken Gravy Mix Over The Steaks To Make A Dry Coating. Stir Any Excess Dry Gravy Mix Into The Slow Cooker. Heat Olive Oil In A Heavy Skillet Over Medium Heat. Pan-Fry The Steaks In The Hot Oil Until Browned On Both Sides, About 8 Minutes. Place The Steaks Into The Gravy Mix In The Slow Cooker, Spooning Gravy Over The Steaks To Moisten. Cook The Onion Rings In The Hot Skillet Until Browned, About 10 Minutes, Stirring Often, And Spread The Onions Over The Steaks In The Cooker. Recover The Cooker, And Cook Until Meat Is Very Tender And The Gravy Is Thick, About 5 Hours.