Heat olive oil in a skillet over medium heat, then add grated onion and cook until soft (about 3 minutes). Stir in minced garlic and sauté for an additional minute. Set aside to cool for 5 minutes.

In a large mixing bowl, combine breadcrumbs, milk, eggs, red wine vinegar, oregano, mint, and a pinch of salt and pepper. Fold in the cooled onion and garlic mixture gently. Carefully add the ground beef and mix just until combined.

Preheat your oven to 350°F (175°C). Shape the burger mixture into patties, about 3/4-inch thick. Place them on a lined baking sheet, ensuring there's space between each for even cooking.

Bake the patties in the oven for 20 minutes or until the internal temperature reaches 160°F (71°C). You want the edges to be crispy and the centers juicy!

Serve the juicy Greek Bifteki Burgers immediately with a squeeze of fresh lemon juice. Pair with tzatziki sauce, warm pita, or enjoy them on toasted buns!