Cooking a beef roast is a pretty forgiving process. You can slap just about any beef roast in the oven at just about any temperature, and sooner or later it will reach the right stage of doneness. That being said, a convection oven can usually make your roasts better and do it in less time.
How Convection Ovens Work
Most ovens have elements at the top and bottom, which heat the air and transfer that heat into the foods you're cooking. Ordinarily, the lower element does most of the work, because hot air rises and as it rises from the bottom element, it naturally circulates across the food and then back down the oven.
Convection ovens turbocharge that natural circulation of air by adding a fan. The fan circulates hot air around the oven more quickly and effectively, and moving air transfers warmth better than still air. You've probably experienced this outdoors, depending on the weather. A hot, dry wind can make you feel like you're about to melt, while a cold wind transfers warmth from your body into the winter air.
The best convection oven models don't just circulate the oven's existing supply of hot air. They actually have additional heating elements in front of the fans, so the fans have a direct supply of newly heated air to push around the oven. When used correctly, a convection oven heats more quickly and evenly than a conventional oven.
Adjusting for Convection Oven Roast
Roasting beef in a convection oven is a bit different from roasting in conventional ovens. There are a couple of adjustments you'll need to make to any recipe that wasn't written with convection in mind. First, because it heats more effectively, you'll usually need to turn down the temperature by about 25 degrees Fahrenheit. For the same reason, you'll need to shorten the cooking time by up to 25 percent, depending on the cut and your cooking temperature.
Finally, convection roasting causes quick browning. That's excellent when you're preparing a small and tender cut that only needs a short cooking time, but not so good for long-cooking pot roasts, which might get over-darkened and leathery at the surface. For those, you might opt to only use convection mode near the beginning or end of your cooking time to keep your browning at an appropriate level.
Cooking Tender Roasts
For small and tender roasts, quick cooking is your best bet in a convection oven. You usually won't need to sear your roast first or start it at a high temperature because convection browns quickly enough to make that extra step unnecessary. With convection, 350 to 375 F is usually plenty hot enough to give good browning, while still keeping your beef tender and juicy.
Follow this for flat cuts, like a strip loin roast or a small piece of prime rib, or for small cylindrical cuts like tenderloin. Even a relatively tough and lean eye of round roast works well when prepared this way, though you'll need to slice it thinly.
For larger roasts, like a full standing rib roast or a big outside round, you'll want to turn the temperature down and cook for a longer time. Actual cooking time will depend on the temperature you choose. One commercial recipe suggests 250 F for up to 8 hours, for example.
Your best bet is to use a thermometer, at least the first few times, to get the doneness you want. Many convection ovens have a built-in probe to let you know when your beef is done, or you can use a leave-in meat thermometer and check it frequently as you cook.
Cooking Pot Roasts
For tougher cuts, like chuck or brisket, it's sometimes smarter to not use your oven's convection mode or at least use it sparingly. Most pot roast recipes call for browning the beef before slow-roasting it in the oven, but you can skip that step with convection. Just turn the convection on for the first 20 or 30 minutes, or the last 20 or 30 minutes, and otherwise cook the pot roast exactly as you would in a conventional oven.