Amigo has the fastest solution. But if you make a lot of these and have to assemble bolts into them, it may be worth the trouble to create a pattern table. The only true benefit a pattern table would provide is reference pattern capabilities for any components assembled into the holes.
I would suggest using patern relations(not to be confused with regular prt/asm relations)The holes would then be put in as expected, in a ring around the part. This is similar to pattern table, but with patern tables each hole is not related to the other ones.
For information on pattern relations Refer to an article called Ptterning the Impossible