Step 1

Heat oil in a large nonstick skillet over medium heat. Add onion and corn; cook, stirring, until the onion begins to brown, about 5 minutes. Coarsely chop 1 tomato. Add it to the pan along with rice, beans, chili powder, 1 teaspoon oregano and 1/4 teaspoon salt. Cook, stirring frequently, until the tomato cooks down, about 5 minutes. Let cool slightly.

Step 2

Coarsely chop the remaining 3 tomatoes. Combine with cilantro, salsa and the remaining 1/2 teaspoon oregano in a medium bowl.

Step 3

Toss lettuce in a large bowl with the bean mixture, half the fresh salsa and 2/3 cup cheese. Serve sprinkled with tortilla chips and the remaining cheese, passing lime wedges and the remaining fresh salsa at the table.