Heat a well-seasoned 9 or 10-inch cast iron skillet over medium heat until hot, about 5 minutes. Add the oil and swirl around the pan. Add the turkey and cook, breaking up the meat, until just cooked through, about 3 minutes. Sprinkle the taco seasoning over the meat and cook according to package directions. Make sure to add a little more water if necessary to keep it saucy. Remove from the heat and stir in the grapes.

Place 2 cups salad greens into each of four wide shallow bowls. Divide the meat mixture among the bowls. Sprinkle cheese and scallions on top, and finish with a squeeze of lime juice. Lightly crush about 4 tortilla chips around the edge of each portion, and top each with a heaping tablespoon of yogurt.