Catalyzes the formation of O-acetylserine (OAS) from L-serine and acetyl-CoA. To a lesser extent, is also able to use succinyl-CoA and propionyl-CoA as acyl donors, but not butyryl-CoA. Does not acylate D-serine and L-homoserine. acetyl-CoA + L-serine = CoA + O-acetyl-L-serine Amino-acid biosynthesis; L-cysteine biosynthesis; L-cysteine from L-serine: step 1/2. Is able to complement an E.coli cysE mutant strain but not an E.coli metA mutant. Belongs to the MetA family.