01 - Preheat an outdoor grill or grill pan over medium-high heat until properly hot.
02 - In a small bowl, whisk together the olive oil, balsamic vinegar, minced garlic, dried oregano, dried thyme, sea salt, and black pepper until well combined.
03 - Brush both sides of the eggplant and tomato slices generously with the marinade. Let them stand for 10 minutes to absorb the flavors.
04 - Place 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 tomato slices for 2 to 3 minutes per side, just until lightly charred but still holding their shape.
06 - Layer the grilled eggplant, tomatoes, and red onion on a serving platter. 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.