Spray the inside of a 3-5 quart slow cooker with nonstick cooking spray. Place the sliced onions in the slow cooker. Combine flour, garlic powder, onion powder and pepper in a large resealable plastic bag. Add steaks, a few at a time; shake until completely coated. Heat the oil in a large skillet over medium heat. Add the steaks, a few at a time, and cook until lightly browned on each side. Place the browned steaks on top of the onions in the slow cooker. Pour 2 c. water over all. Cover; cook on Low for 8 hours or until meat is tender. In a bowl, whisk together the 3 gravy mixes with remaining 1 c. water. Add to slow cooker; cover and cook on Low for 30 minutes longer. Serve over mashed potatoes, rice or noodles. 6 servings.