Place rinsed quinoa and water in a medium saucepan over high heat. Once it reaches a rolling boil, reduce heat to low and cover. Simmer for 12-15 minutes until liquid has absorbed completely and quinoa appears fluffy with visible white rings. Remove from heat and let stand covered for 5 minutes, then fluff with a fork.

While quinoa cools to room temperature, dice cucumber into uniform half-inch pieces. Chop tomatoes into similar-sized chunks. Finely dice the red onion and roughly chop the fresh herbs.

In a small bowl, combine olive oil, fresh lemon juice, minced garlic, salt, and pepper. Whisk vigorously for about 30 seconds until mixture becomes slightly thick and creamy. Taste and adjust seasoning as needed.

Add cooled quinoa to a large mixing bowl along with all prepared vegetables and herbs. Pour dressing over mixture and toss gently but thoroughly. Add crumbled feta last, folding it in carefully to maintain chunky pieces.