Catalyzes the formation of fatty acid-cholesterol esters, which are less soluble in membranes than cholesterol (PubMed:11294643, PubMed:16647063). Plays a role in lipoprotein assembly and dietary cholesterol absorption (PubMed:11294643). Utilizes oleoyl-CoA ((9Z)- octadecenoyl-CoA) and linolenoyl-CoA ((9Z,12Z,15Z)-octadecatrienoyl- CoA) as substrates (PubMed:11294643). May provide cholesteryl esters for lipoprotein secretion from hepatocytes and intestinal mucosa (PubMed:11294643). {ECO:0000269|PubMed:11294643, ECO:0000269|PubMed:16647063}. [Isoform 2]: Has lower enzymatic activity compared to isoform 1. . [Isoform 3]: Has lower enzymatic activity compared to isoform 1. . This is the function of SOAT2 (sterol O-acyltransferase 2, Ensembl gene identifier ENSG00000167780).