In a medium saucepan, combine the quinoa and water or vegetable broth. Bring to a boil over medium-high heat.
Reduce the heat to low, cover, and simmer for 15 minutes, or until the quinoa is tender and the liquid is absorbed. Remove from heat and let it cool.
Preheat the grill to medium-high heat.
In a large bowl, toss the sliced zucchini, yellow squash, red bell pepper, red onion, and corn with 2 tablespoons of olive oil, salt, and pepper.
Grill the vegetables for 5-7 minutes on each side, or until they are tender and slightly charred. Remove from grill and let them cool slightly.
Cut the grilled vegetables into bite-sized pieces and cut the corn kernels off the cob.
In a large bowl, combine the cooked quinoa, grilled vegetables, remaining 1 tablespoon of olive oil, balsamic vinegar, dried oregano, and chopped basil. Toss to combine.
Serve the salad warm or at room temperature, topped with crumbled feta cheese if desired. Enjoy!