Rinse and drain the strawberries and place them in a food processor or blender. Add the yogurt, orange juice, and sugar. Process on the highest speed until the mixture is a well-blended purée, about 15 seconds, stopping to scrape down the sides of the container once or twice. Taste the mixture and sweeten with a little more sugar, if you wish.
For a very smooth beverage, strain the mixture, using a wooden spoon to push the drink through. Discard the strawberry seeds.
Pour into 4 tall glasses and serve immediately. If you wish to decorate the drinks, slit some strawberries and orange slices halfway through the centres. Garnish each glass with the fruit.
Per serving: 108 calories, 4 g protein, 2 g total fat, 1 g saturated fat, 5 mg cholesterol, 21 g carbohydrates, 4 g fibre.