Moo Shu Beef Lettuce Cups

spray(s) cooking spray (5 one-second sprays per serving)

pound(s) uncooked 93% lean ground beef

cup(s) uncooked onion(s) yellow, thinly sliced

ginger root fresh, minced

clove(s), medium garlic clove(s) minced

cup(s) uncooked bok choy thinly sliced

medium sweet red pepper(s) thinly sliced

cup(s) button mushrooms thinly sliced (about 10 mushrooms)

low sodium soy sauce

leaf/leaves bibb lettuce