Easy Beef Tips in Mushroom Sauce

2 lbs lean chuck, cut into 1 & 1/2 inch pieces
1 can cream of mushroom soup
1 pkg. onion soup mix (Lipton)
1 c. 7-up
1 can mushrooms

Place meat in a 2-quart casserole dish. Do not season. Combine soup and dry soup mix and pour over the meat. Add 7-up. Cover and bake at 275 degrees for 4 hours. During cooking, do not open oven door. After 4 hours, remove from oven and let stand for 30 minutes before serving. Serve over noodles or rice.