This recipe is from The Frugal Gourmet Cooks Italian by Jeff Smith (Wm. Morrow, 1993).
Peel the lemons, using a potato peeler, making sure not to remove any of the white pith. This should yield about 1 cup of lemon peel. Save the peeled lemons for juice in other dishes. Place the peel in a mortar along with 1/4 cup of the olive oil. With the pestle, pound and rub the peel and oil together for one minute. Remove to a 2 quart glass jar or sealed plastic container and add 3 3/4 cups additional olive oil. Allow to marinate four days at room temperature. Strain the oil and discard the peel. Makes 4 cups.