Would a Catholic irregular session marriage at St. Andrews in Glasgow on 25/11/1821 be listed in the OPR? I believe these are my 3x-g-gp Donald McDonald, Tailor, and Mary Crerar.
The primary purpose of the OPRs was to record baptisms, marriages and (if you are really, really lucky) burials carried out by a Church of Scotland minister in that parish. While there seems to have been some sort of intention that all births / baptisms and marriages should be recorded, in all my families (I'm 1/8 Scottish descent) I've only ever seen this happen for one family in one parish.
If I examine the page of marriages that you posted, virtually every entry records a non CofS minister - Burgher ministers, Relief ministers, presumably the Gaelic ministers as well. It's therefore quite clear that this page represents part of some sort of attempt to record all marriages in the parish. So it's perfectly possible that a Catholic marriage would be recorded there.
What I'm less certain of is the exact meaning of the phrase used for their entry. "St. Andrew's Session" will surely refer to the Kirk Session of a Church of Scotland church called St Andrew's. (Logically, you should check that one of that name exists in the area.) Not to a Catholic church. Irregular marriages were unions that had not taken place according to the rules of the CoS. Marriage By Repute is one example where the couple live together without a ceremony taking place but everyone actually believes that they are married. (Not the same as just living together).
Whether a Catholic ceremony would be rudely dismissed as Irregular just because it was Catholic, I have no idea. If you could get hold of the relevant Kirk Session records (Scotlands People is supposed to be releasing them sometime) then they might shed light on the reason, because I guess that they discussed the matter and had the marriage recorded in the OPR. The date is probably just the date that the Kirk Session discussed the matter or the OPR entry was made.
So the Session in question is probably just the body making the report of what it saw as an irregular marriage.
I take it that you've checked the RC records on Scotlands People?
Thanks for your detailed response. The sources and sites that I consulted gave conflicting and vague answers. I have checked Scotlands People RC records but there was nothing to be found. You've provided the most clarity. Dec 4, 2020 at 21:09
1I see that in 1801 there were 8 parish churches in Glasgow (sc. of the Established Church), one of which is St Andrew's. But the RCs also have a St Andrew's Church dating from 1816 ish; and the Episcopalians also have a Chapel at St Andrew's Square, near the parish church. However I'd agree that the phrase "St Andrew's Session" can only apply to a presbyterian denomination, and almost certainly to the Parish Church Session. Dec 17, 2020 at 11:30
According to this page, the Church of Scotland seems to have recorded all marriages.
Before the introduction of civil registration in 1855 Church of Scotland parish ministers and session clerks kept registers of births and baptisms, proclamations of banns and marriages, and deaths and burials.
Thus, I'd say yes to "Would a Catholic irregular session marriage at St. Andrews in Glasgow on 25/11/1821 be listed in the OPR?"
1In practical terms, as I say in my answer, while there might have been an intention, it was far from successful. As it says on the same page: "They [OPRs] are far from complete". Nevertheless, the parish on the page does seem to have, at this point, have covered more than just the Church of Scotland. I just don't want anyone to get the wrong idea about coverage. Dec 4, 2020 at 20:22
@AdrianB38 to expect complete coverage anywhere except a fully bureaucratic state is folly, and no country was that developed before at least 1900.– RonJohnDec 4, 2020 at 21:01