I'm not sure if someone has already said this but it depends on your usage of the word!
If you're using it to mean the food, then you wouldn't pluralize beef. Instead, you would say "I had two different types of beef" or "I had double the beef" or something.
If you meant it like having a gripe with someone, it would be beefs.
"I have beefs with people all over town"
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While it seems like I'm responding to myself, actually this is Trinick arguing with neonfallout about her grammar.
You wouldn't say "I have beefs with people all over town" because that would imply that for each individual throughout the town, you have more than one beef. You would say "I have beef with people all over town." Furthermore, the plural of beef is technically beeves, not beef. However, you're right in that 99% of the time you would use the singular form with the plural on a different word, like "two cuts of beef" or "many plates of beef."