Arugula and Watermelon Salad

2 (5 ounce) packages arugula

½ large watermelon, seeded and cubed

1 red onion, sliced

1 cup crumbled feta cheese

1 ½ cups balsamic vinaigrette

Toss the arugula, watermelon, red onion, and feta cheese with the balsamic vinaigrette in a large bowl. Serve cold.