Preheat and prep: Heat the oven to 425°F (220°C).
Line a large sheet pan with parchment for easy cleanup.
Season the veggies: Chop the peppers and zucchini into thick strips or chunks. Slice the red onion into wedges. If using eggplant, cut into half-moons.
Toss everything with 2–3 tablespoons olive oil, 2 minced garlic cloves, 1 teaspoon dried oregano, 1/2 teaspoon dried thyme, 1 teaspoon lemon zest, 1/2 teaspoon red pepper flakes (optional), and a big pinch of salt and pepper.
Roast: Spread the veggies on the sheet pan in a single layer. Roast for 15 minutes, then add the cherry tomatoes, toss, and roast another 10–15 minutes until tender and caramelized at the edges.
Season the beef: While the veggies roast, pat the steak dry. Rub with 1–2 tablespoons olive oil, remaining minced garlic, 1 teaspoon dried oregano, 1/2 teaspoon dried thyme, lemon zest from the rest of the lemon, and generous salt and pepper.
Let it sit at room temperature while the veggies finish.
Sear the steak: Heat a heavy skillet (cast iron works best) over medium-high until very hot. Sear the steak 2–4 minutes per side, depending on thickness and desired doneness. For medium-rare, aim for an internal temperature of 130–135°F (54–57°C).
Rest and slice: Transfer the steak to a board and rest 5–10 minutes.
Squeeze half the lemon over the top. Slice thinly against the grain.
Finish the veggies: Toss the roasted vegetables with the remaining lemon juice and a splash more olive oil. Sprinkle with chopped parsley.
Add olives and crumbled feta if you like.
Serve: Pile the roasted veggies onto plates, top with the sliced beef, and finish with a dollop of yogurt or tahini. Serve with warm pita or over couscous for a fuller meal.