In a medium bowl, combine olive oil, minced garlic, lemon juice, oregano, thyme, salt, and pepper. Whisk until blended, then add the sirloin steak, ensuring it's fully coated. Marinate in the refrigerator for at least 30 minutes.

In a separate bowl, mix Greek yogurt, grated cucumber, lemon juice, garlic, and dill. Season with salt and pepper, stir well, and let refrigerate for at least 15 minutes.

In a small bowl, whisk together olive oil, lemon juice, honey, minced garlic, and seasonings to create vinaigrette. Let the flavors infuse.

Heat a skillet over medium-high heat and cook the marinated steak for 4-5 minutes on each side. Rest the steak for 5 minutes before slicing thinly against the grain.

Assemble the Mediterranean Steak Bowl by layering cooked grains, sliced steak, fresh vegetables, tzatziki sauce, and vinaigrette. Sprinkle with feta if desired.