I don't ever remember doing pre interview social events at a country club. I guess it is little different by region.
All the pre interview events I went to were cocktail social kinda thing. We were all dressed up in business attire minus tie etc.
I also remember getting invited to all day event at HQ after receiving an offer with breakfast and lunch to wow us (and convince us that we should accept the offer).....
My instinct says that you should still dress up professionally but it wouldn't hurt to email the recruiter and ask for a tip.
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