Because you don't need to soak lentils, cooking them takes very little time. Brown and green lentils, found in most U.S. supermarkets, are ready in 20 to 30 minutes. After 20 minutes, lift several beans from the pot, rinse them under cold water and test for doneness. They should be completely tender when you bite into them. Cook them as an ingredient in lentil burgers or as additions to a variety of meals, such as mixed with rice or vegetables. Or add uncooked lentils directly to vegetable soups, where they will cook in about the same time as carrots and potatoes.