Catalyzes the formation of fatty acid-cholesterol esters, which are less soluble in membranes than cholesterol. Plays a role in lipoprotein assembly and dietary cholesterol absorption. In addition to its acyltransferase activity, it may act as a ligase. Utilizes oleoyl-CoA and linolenoyl-CoA as substrates. May provide cholesteryl esters for lipoprotein secretion from hepatocytes and intestinal mucosa.