Boil cabbage in large pot in salted water. Be sure to boil cabbage long enough so inner leaves are soft enough to work with, approximately 40-45 minutes.
Prepare rice according to package directions and let cool.
Mix ground beef, rice, onion, salt, pepper and egg.
After cabbage is softened, drain and let cool in colander. Gently peel off one cabbage leaf at a time. On flat surface, lay out cabbage leaf. Take some of meat/rice mixture and form into oval shaped patty. Place on cabbage leaf near base of stem. Fold left side and right side of cabbage leaf over meat/rice mixture, then roll up.
Place seam side down in baking dish or roasting pan. Stuffed cabbages can be layered in pan. Cook in your favorite spaghetti sauce at 350 degrees for 45-60 minutes, depending on your oven, until meat is thoroughly cooked and no longer pink.