- Cut the zucchini and yellow squash lengthwise into 1/4 inch slices. Arrange the slices on a platter or in a baking dish and sprinkle both sides with the garlic, oregano, mint, hot pepper flakes, and lots of salt and pepper. Drizzle 2 tablespoons oil over them, turning the slices several times to coat both sides. Let marinate for 15 minutes.
- Set up the grill for direct grilling and preheat to high. If using a vegetable grate, preheat it as well. If using a gas grill, place the wood chips, if desired, in the smoker box or in a smoker pouch and preheat until you see smoke.
- When ready to cook, if using a charcoal grill, toss the wood chips, if desired, on the coals. Arrange the zucchini and yellow squash slices on the hot grate and grill until nicely browned on both sides, 4 to 6 minutes per side, rotating the slices 90 degrees after 2 minutes on each side to create an attractive crosshatch of grill marks.
- Transfer to a platter. Drizzle the remaining 1 tablespoon of oil over the zucchini and yellow squash and garnish with lemon wedges, if using. Serve at once.