Here's one easy tip that will quickly improve your next BBQ. Now there's nothing wrong with Costco, they usually have excellent quality; however, for some reason their frozen burgers aren't that great. Smart and Final actually has the best frozen burger patties I've seen, aside from grinding meat and making your own patties.
It's the same price (or sometimes cheaper) and another benefit is that they are IQF (individually quick frozen) - patties don't stick to one another. In my opinion, they taste alot better than Costco burgers. Smart and Final sells them in white boxes under the brand "First Street" and are differentiated by the fat content. I usually just get the cheapest. Another thing to look out for is the numbers such as 4/1. What this means is 4 patties per pound (or 1/4lb patties). They sell in 10lb boxes so you can buy 40 patties for the same price as 50 smaller patties or 30 larger patties. My recomendation is to do the standard 1/4lb.