Brown ground beef and drain off fat. Mix well with mushroom soup and rotel tomatoes.
Line bottom of slow cooker with 1 cup of corn chips. Add 1/3 of onion, sprinkle with 1/3 of grated cheese and add 1/3 of meat mixture. Repeat layers, cover and cook on low 6-8 hours or on high 3 hours.
You may also bake in a casserole at 325 degrees for 45 minutes.