Line a baking tray with baking paper. Cut the grapes into small bunches. Put the coconut into a bowl.
Heat the chocolate in a small microwave-safe heatproof bowl, uncovered, in 1 minute bursts on High/100%, stirring every minute with a metal spoon until warm and just melted.
Dip grapes 1 bunch at a time into the warm chocolate, shaking off the excess. Sprinkle over the coconut. Put onto tray. Refrigerate until set. Serve.