Preheat your Oven to 375°F. In a large Mixing Bowl, whisk together the 10 large egg whites from fresh eggs or carton egg whites, ¼ cup low-fat milk, ¼ tsp ½ tsp kosher salt divided, and ¼ tsp black pepper freshly ground until frothy and well combined, about 1 minute. Set aside.

Heat the 1 tbsp olive oil in a Skillet over medium heat. Add the diced 1 medium red bell pepper diced and 1 medium zucchini diced small and cook, stirring occasionally, until softened, about 4–5 minutes. Add the minced 3 cloves garlic minced and cook for 30 seconds until fragrant. Add the 2 cups baby spinach roughly chopped and remaining ¼ tsp ½ tsp kosher salt divided, stirring until wilted, about 1 minute. Scatter the ½ cup cherry tomatoes halved evenly across the vegetables.

Reduce the heat to medium-low. Pour the 10 large egg whites from fresh eggs or carton egg whites mixture evenly over the vegetables in the Skillet. Sprinkle the crumbled ⅓ cup crumbled feta cheese reduced-fat if preferred over the top. Let the frittata cook undisturbed on the stovetop for 3–4 minutes, until the edges just begin to set.

Transfer the Skillet to the preheated Oven and bake for 10–12 minutes, until the center is fully set and the top is lightly golden. Remove from the Oven and let rest for 2–3 minutes before slicing. Garnish with fresh 2 tbsp fresh chives thinly sliced, for garnish and serve warm directly from the Skillet.