Cooking Roast Beef to Perfection
The very rosy, red color of rare roast beef isn't the best indicator of doneness. For the most accurate measurement, you need to check the temperature of the meat with a meat thermometer and remove the meat just before it reaches the desired temperature. Slices on the outer edges of the roast, which cook more quickly than the center of the roast, will have a different temperature.
Using an Instant-Read Thermometer
Instant-read and oven thermometers come in a variety of styles, but some general rules apply to all kinds. Take your time when measuring the temp of the beef. Remove the roast from the oven; set it on the stovetop, and insert the instant-read thermometer sideways into the beef so that the tip of the thermometer rests in the center of the roast. When the temperature on any thermometer registers five to 10 degrees lower than the desired temperature – 125F for a rare roast – cover the meat with foil, and let it rest on the stovetop. The meat will briefly continue to cook, and the temperature will continue to rise as the roast rests.
Temperatures Throughout the Roast
Because the outer parts of the roast cook more quickly than the center, temperatures will vary even while you cook the entire roast to rare. With a rare roast, the meat at the very center of of the roast feels cool to the touch and is very red. The sections around the center will also be rosy red, but will be warm and register about 135F. As you move from the center, the meat will be cooked to medium, with a pink color, at 145F; to medium well, slightly pink and 150F; and finally at the edges, to well done, with only a very slight amount or no pink at all and a temperature of 160F.
U.S. Department of Agriculture Recommendations
Cooking kills some harmful bacteria found in meats and other foods, and for that reason, the USDA recommends that all beef be cooked to a temperature of 145F and that ground beef be cooked to 160F. To ensure that all sections of the meat reach the safe temperature, the USDA goes on to say that you should let all meat rest for at least 3 minutes once it's out of the oven. Because ovens vary in temperature, you can't rely on cooking times alone to ensure that your roast is cooked thoroughly.