Step 1

Using large piece of heavy-duty aluminum foil, wrap wood chips in 8 by 4½-inch foil packet. (Make sure chips do not poke holes in sides or bottom of packet. If using gas, make sure there are no more than 2 layers of foil on bottom of packet.) Cut 2 evenly spaced 2-inch slits in top of packet.

Step 2

FOR A CHARCOAL GRILL: Open bottom vent halfway. Light large chimney starter mounded with charcoal briquettes (7 quarts). When top coals are partially covered with ash, pour two-thirds evenly over half of grill, then pour remaining coals over other half of grill. Place wood chip packet along 1 side of grill near border between hotter and cooler coals. Set cooking grate in place, cover, and open lid vent halfway. Heat grill until hot and wood chips are smoking, about 5 minutes.

Step 3

FOR A GAS GRILL: Remove cooking grate and place wood chip packet directly on primary burner. Set cooking grate in place, turn primary burner to medium, and turn other burner(s) to high. Cover and heat grill until hot and wood chips are smoking, 15 to 25 minutes. Leave primary burner on medium and other burner(s) on high.

Step 4

Clean and oil cooking grate. Brush corn with oil. Grill corn, poblanos, and Fresnos on hotter side of grill (covered if using gas) until corn is charred on all sides and poblanos and Fresnos are well blistered, 5 to 10 minutes. As poblanos and Fresnos finish cooking, transfer to bowl, cover tightly with aluminum foil, and let sit until skins soften, about 5 minutes. Transfer corn to cutting board. Turn all burners to medium (if using gas).

Step 5

Cut kernels from corn. Using paper towels, peel away skin from poblanos and Fresnos. Slice poblanos into 1/4-inch-thick strips and thinly slice Fresnos. Combine corn, poblanos, Fresnos, black beans, Monterey Jack, and cheddar in bowl.

Step 6

Spread one-quarter of tortilla chips evenly in 12-inch cast iron skillet. Sprinkle with one-quarter of vegetable-cheese mixture. Repeat layering of chips and vegetable-cheese mixture 3 more times. Place skillet on cooler side of grill (if using charcoal), cover, and cook until cheese is melted, 15 to 30 minutes. Sprinkle with scallions and serve with lime wedges.