Pull the marrow out of the bones. Season the marrow with salt and pepper and coat with flour. Let the marrow sit in the flour for 10 minutes, and then dust the flour off.
Heat a small sauté pan under medium heat and add the vegetable oil.
Sauté the marrow until it turns golden brown. About 4-5 minutes. Toss in grapes, and finish cooking with the lid on for another 1 minute. Season with salt and freshly ground pepper.