Preheat oven to 200 degrees celsius. Put the rhubarb, Equal, vanilla and ginger into a pan, pour over 1/4 cup water. Cook covered over a medium heat for 10 minutes or until the rhubarb is just soft. Do not overcook or it will become mushy. Spoon the rhubarb mixture into a 6-cup capacity ovenproof dish.
Put the oats, flour, Equal and margarine into a bowl and rub lightly with your fingertips until the mixture resembles large breadcrumbs. Sprinkle over the rhubarb mixture. Bake in a non-stick baking tray for 30 minutes or until the crumble is crisp and golden.
Try adding 200g fresh or frozen raspberries to the crumble for extra flavour. Serve with low fat custard.