With the rack in the lowest position, preheat the oven to 180 ºC (350 ºF). In a bowl, combine the rhubarb, sugar, cream and vanilla extract. Pour into an ungreased 30 x 20-cm (12 x 8-inch) baking dish.
In another bowl, blend the oats, brown sugar, flour and butter.
Scatter over the rhubarb mixture. Bake for about 50 minutes or until the crisp is golden brown. Serve hot, warm or cold. Serve with ice cream.