Start by cutting your watermelon into roughly 1-inch cubes. You want pieces that are big enough to hold their shape on the grill but not so large that they become cumbersome to eat.
Heat your grill or grill pan to medium-high heat. If you’re using an outdoor grill, lightly oil the grates to prevent sticking.
Toss the watermelon cubes gently with 1 tablespoon of olive oil. Place them on the grill and cook for about 2-3 minutes on each side. You’re looking for nice grill marks and a slight caramelization but be careful not to overcook as watermelon can become mushy.
In a small bowl, whisk together the remaining 2 tablespoons of olive oil, balsamic vinegar, salt, and pepper. Adjust the seasoning to your preference.
Transfer the grilled watermelon to a large bowl. Add the crumbled feta and chopped mint leaves. Drizzle the dressing over the top and toss gently to combine everything without breaking the watermelon cubes.
Serve immediately to enjoy the contrast of warm, smoky watermelon and cool, creamy feta. This salad is perfect as a side dish or even a light main course on a hot day.