Place quinoa in a small saucepan and add ½ cup water. Bring to a boil over medium-high heat. Reduce heat, cover and simmer for 15 minutes or until water is absorbed. Let cool slightly.
Add watermelon and feta to a large mixing bowl. Add cooled quinoa, stir to combine. Add lime juice and olive oil; toss to coat. Top with chopped mint and serve.
Notes
If preparing prior to serving, wait to add the mint until just before serving.