Is refrigerated ground chuck safe to eat 4 days past sell by date?

No, it is not safe to eat refrigerated ground chuck that is 4 days past its sell by date. Ground chuck is a highly perishable food that can quickly spoil and become unsafe to eat. The sell by date is the last day that the product is recommended for sale, but it does not mean that the product is unsafe to eat after that date. However, the quality of the meat will start to decline after the sell by date, and it may become unsafe to eat within a few days.

Ground chuck should be cooked to an internal temperature of 160°F to kill any harmful bacteria. If you are not sure whether the meat is still safe to eat, it is best to err on the side of caution and discard it.