How much margarine was rationed during World War 2?

None! Margarine wasn't purchased by the government during World War 2, thanks mostly to lobbyists in the butter industry. So it wasn't subject to rationing, which made it cheaper and more abundant than butter. It backfired on the butter industry, because after WW2 almost everyone used the non-rationed margarine and butter has since been more expensive and less purchased. Good question.