Place onion and oil in a 1 cup measure. Cover with plastic wrap. Microwave at high (100%) until onion is tender, 1 to 2 minutes. In mixing bowl combine beef and onion/oil and mix well. Divide the mixture into four equal parts. On a sheet of wax paper flatten each part into an oblong shape about 3/4 of an inch thick and divide in half. Top one half with a piece of cheese. Cover with other half and seal edges together around the cheese firmly. Repeat with other equal parts. Sprinkle with seasoned salt and seasoned pepper. Place hamburger steaks on a rack set in 8 x 12 baking dish. Cover with wax paper. Microwave at high (100%) 5 minutes. Turn hamburger steaks over. Cover with wax paper. Microwave at high (100%) 5 to 6 minutes. Let stand, covered, 2 to3 minutes. Makes 4 servings