In a small saucepan, heat 1 tablespoon of the vegetable oil. Add the garlic and cook over moderate heat until fragrant, about 1 minute. Add the chile powder, vinegar, 1 teaspoon of the oregano, and 3/4 cup of water and cook over very low heat, whisking occasionally, until the marinade is slightly thickened, about 3 minutes. Season with salt. Transfer the marinade to a large baking dish and let cool completely. Add the steaks and turn to coat. Cover and refrigerate overnight.

Light a grill. In a large saucepan, heat the remaining 1 tablespoon of oil. Add the chorizo and cook over moderate heat until crisp, about 4 minutes. Using a slotted spoon, transfer the chorizo to a bowl; reserve it for another use. Add the onion to the saucepan along with the remaining 1/2 teaspoon of oregano and cook until softened, about 6 minutes. Add the beans with their liquid and simmer until slightly thickened, about 10 minutes. Season lightly with salt.

Grill the rib eye steaks over moderately high heat, turning once, about 12 minutes for medium-rare meat. Serve the steaks with the black beans, avocado slices and lime wedges.

The ancho-chile marinade can be refrigerated for up to 1 week. The cooked black beans can be refrigerated for up to 2 days.