If you plan to make the burger bowl salad ahead of time, you can freeze the seasoned beef mixture for later use:   After browning the ground beef, let it cool completely.   Divide the cooled mixture into portions and store them in freezer-safe containers or zip-lock bags or vacuum sealed bags.   Frozen ground beef will generally stay safe for up to 3 months. Thaw the mixture completely in the refrigerator before using it in your burger bowl salad.