Wipe the chicken drumsticks dry and place in a large resealable bag.
Lightly pound and peel the garlic.
Pour the vinegar and soy sauce into the resealable bag. Add the garlic, peppercorns, bay leaves and oregano. Seal the bag. Shake a few times to distribute the seasonings. Keep the in the fridge overnight.
Pour water into a steamer and boil.
Drain the chicken then arrange in the steamer basket(s) in a single layer.
Steam the chicken over briskly boiling water for 10 minutes.
Remove the steamer baskets and cool the steamed chicken.
Heat the cooking oil in a frying pan.
Over medium-high heat, fry the cooled steamed chicken adobo just until crisp.
Serve the fried chicken adobo with rice.