Drain the juice from one can of beans. Pour the drained beans into a bowl. Use a potato masher to mash the beans until they are no longer whole. Set the mashed beans aside.
Chop the onion in to 1/4-inch pieces. Set it aside. Peel the garlic cloves and mince them finely. Set the garlic aside.
In a medium saucepan, heat the oil over medium high heat. Add the onions and sauté for 1 to 2 minutes. Stir in the garlic and cumin and cook for 30 seconds more.
Stir in the mashed black beans and the second can of black beans, including the juice. When the beans begin to boil, reduce the heat to low, stir in the oregano and simmer for 10 minutes, uncovered.
