Drain and rinse beans.
Pour oil to a large stock pot and heat over medium-high heat.
Add grated onion and garlic with their juices, along with the beans, oregano, cumin and beer. It will be foamy.
Stir together and let come to a boil to cook out the alcohol.
Once it no longer smells like freshly poured beer, reduce heat and simmer until liquid is almost reduced by half. Stir occasionally to prevent sticking.
Taste for seasoning, adjust as needed.