Eye of round roast is the most tender cut of meat from the round, but it has very little fat, which means it can dry out and become tough while cooking if you're not watching the time. The length of time to cook the roast depends on the size of the cut of meat, how well you want it cooked and how you cook it--in a roasting pan or in an oven bag.
Weigh the eye of round roast on the kitchen scale.
Multiply the roast's weight by 35 to 38 minutes for rare, 35 to 45 minutes for medium-rare, 45 to 53 minutes for medium, 45 to 60 minutes for medium-well and 55 to 68 minutes for well-done if you're going to cook the eye of round roast in a roasting pan. A 3-lb. roast cooked to medium would take about 2 hours, 45 minutes.
Cook a 2- to 3-lb. roast for 1 hour to 1 hour, 15 minutes and 1 hour,15 minutes to 1 hour, 45 minutes for a 3- to 5-lb. roast if you're using an oven bag.
Determine doneness by temperature. An eye of round roast will continue to cook after you remove it from the oven. The final temperature will determine doneness. Therefore, remove the roast from the oven about 10 degrees F before your desired doneness. The final temperature for rare is 140 degrees; medium-rare is 145 degrees; medium is 160 degrees; medium-well is 165 degrees; and well-done is 170 degrees.