Which is correct? Everyone here at xyz wish you a happy holiday or everyone here at xyz wishes you a happy holiday?
It´s "wishes", since it is in third person (Everyone), so the correct way to say it is: Everyone here at xyz wishes you a happy holiday.
1 Forming the third person singular of the present tense in verbs ending in sibilant sounds.
2 Forming the third person singular of the present tense in verbs ending in -o (but not -oo) ‘goes’
So either way with the subject being "everyone" it is only correct to use "wishes" (verb)
Source from Oxford Dictionaries!
It should be either
Everyone (here at ...) wishes you [...]
since "everyone" is 3rd person singular, or
We (at ...) wish you [...]
since "we" is 1st person plural.