Rating Newest Oldest. Best Answer: Any cooked leftover last 4 days in the fridge. I looked it up on this site: http://www.wisegeek.com/how-long-will-me... Also, you can freeze cooked ground beef and it will last even longer, like up to a month. What i do is wrap cooked ground beef in sran wrap in little packets (about 4 by 4 inches), and pop it in the microwave for 1.5-2 minutes and it tastes just as good as when I first made it.