1/2 cup extra-virgin olive oil
1/4 cup fresh lime juice
1 teaspoon minced garlic
1 tablespoon minced canned chipotle chiles in adobo
3 tablespoons vegetable oil
2 ears of corn, shucked
2 firm-ripe 6-to 8-ounces avocados, halved and pitted but not peeled
1 head romaine (1 pound), tough outer leaves discarded and head quartered lengthwise, then cut crosswise into 1-inch strips
Put parmesan in a medium bowl and add olive oil in a slow stream, whisking. Whisk in lime juice, garlic, chipotles, and 1/4 teaspoon each of salt and pepper.
Rub vegetable oil on corn and cut sides of avocados, then season with 1/8 teaspoon each of salt and pepper. Grill avocados, cut sides down, and corn, turning corn occasionally, until golden-brown, 3 to 4 minutes.
Peel avocados and thinly slice. Cut corn kernels from cobs.
Toss romaine with dressing and serve topped with avocado and corn.