01 - Preheat an outdoor grill or grill pan over medium-high heat until properly heated.
02 - In a small mixing bowl, whisk together the olive oil, balsamic vinegar, minced garlic, dried oregano, dried thyme, sea salt, and black pepper until well combined.
03 - Using a basting brush, coat both sides of the eggplant and tomato slices evenly with the marinade. Let stand for 10 minutes to absorb the flavors.
04 - Place the eggplant slices on the grill and cook for 4 to 5 minutes per side until tender with visible grill marks. Grill the red onion slices at the same time, if using.
05 - Grill the tomato slices for 2 to 3 minutes per side, just until lightly charred but still holding their shape.
06 - Arrange the grilled eggplant, tomatoes, and red onion on a serving platter in alternating layers. Sprinkle with torn fresh basil leaves and crumbled feta cheese, if desired.
07 - Serve warm or at room temperature alongside grilled bread, couscous, or quinoa.