Q. As the holiday season approaches is there a problem with attending or promoting a year’s end party for your employees?

A. The Talmud (Avoda Zarah 8a) mentions that if “an idolater gives a banquet for his son and invites all the Jews in his town, then, even though they eat of their own and drink of their own and their own attendant waits on them, Scripture regards them as if they had eaten of the sacrifices to dead idols, as it is said (Shemos 34:15), And he will call thee and thou wilt eat of his sacrifice”. Shulchan Aruch (Y.D. 152,1) rules accordingly.

Poiskim disagree whether the prohibition applies only to weddings or even to other banquets and feasts. There are also differing opinions if the “heter of eivah” (permission granted to avoid creating hate) applies in this instance or the interdiction to engage in activities leading to intermarriage is more relevant (see Taz and Shach ibid. –  Rambam, Maacholos Assuros 17,10,). Other particulars that should be considered are; who owns the venue, who makes up the majority of the attendants and what manner of behavior, dress and alcohol consumption prevails. (Zera Yaakov 8, p. 96).

Although there are different opinions as to the halachik status of today’s Gentiles, as a general rule, sefer Yesod Yosef  (ch. 81) construes from the Talmud (Megilah 12a) and other sources, that one should avoid when possible the attendance or promotion of such events.

As mentioned there are many variants and details to each particular case, therefore Horav Shlomo Miller Shlit”a advices to consult a competent Halachik authority in each situation.
 
Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a