= Queen's Counsel.
A. Plural Form.
Though some writers make the plural form Q.C.s, the better form is Q.C.'s.
B. Punctuation with.
When the title appears in midsentence, a comma goes before and after it:
“Roman law texts were also cited by Sir Sidney Kentridge, Q.C., counsel for the claimants.”
Basil Markesinis & JÖrg Fedtke, The Judge as a Comparatist, 80 Tul. L. Rev. 11, 96 n.279 (2005).
Some writers omit the periods in this abbreviation—e.g.:
“If a client wants to employ a Queen's Counsel or senior barrister, he must also employ—at two-thirds the QC's fee—a junior barrister as well.”
Anthony Sampson, Anatomy of Britain 149 (1962). The prevailing style—in BrE and AmE alike—is to include the periods.