Sprinkle bottom of crock pot with half the salt and pepper then drizzle 1 tbsp olive oil over the bottom of the pot. Rough chop the onion and spread over the bottom of the pot. Place frozen Cornish game hen on top of the onions. Drizzle the remaining Tbsp of olive oil on the bird. Rough chop the garlic and place half on top of the bird and the rest, let fall in the pot. Season the bird with salt, pepper and garlic & onion seasoning. Top the bird with dried or fresh rosemary.
Add a 1/4 cup of water or white wine to the pot. Cook on low heat setting for 6 hours or until the legs begin to fall away from body.
To serve, cut the bird down the middle.
Optional: Carefully remove the hen from the slow cooker and transfer to a small baking dish. Place in a 450 degree oven just until skin is crispy and golden brown.
Cook 2 hens at a time for a larger family dinner or substitute a whole chicken. Just make sure to increase the cooking time to allow for the larger bird.