Although they're both beef roasts, chuck and sirloin have distinct characteristics. One main difference is section of the cow they originate from. More practically, it's how they're cooked. Chuck roast is a leaner, tougher meat than sirloin, and should be braised at low temperature, over a long period of time. Sirloin is cooked using dry heat. After seasoning with salt, pepper and other spices you like, it's typically doused usually with olive oil, then seared in a hot pan until it has a light brown crust. It is then transferred to a preheated oven or rotisserie until the desired internal temperature is reached; 140 F* medium-rare, 155 F* medium. Our Sirloin and Chuck roasts are hand trimmed USDA "Choice" or better graded beef.