chopped flat-leaf parsley or cilantro
Roast peppers for sauce:
Roast peppers on racks of gas burners on high, turning with tongs, until skins are blackened all over, 10 to 12 minutes. (Or broil peppers on rack of a broiler pan 5 inches from heat, turning occasionally, about 15 minutes.) Transfer to a bowl and let stand, covered, 10 minutes.
Make soup while peppers roast and stand:
Cut kernels off cobs, then scrape cobs with knife to extract “milk.”
Cook onion in oil in a heavy medium pot over medium-high heat, stirring occasionally, until golden, about 5 minutes. Add corn with its “milk,” water, oats, and sea salt and simmer, uncovered, stirring occasionally, 15 minutes.
Peel peppers (do not rinse), then halve lengthwise, discarding stems and seeds.
Purée peppers in a blender with oil, lemon juice, hot sauce, sea salt, and 1/4 teaspoon pepper until very smooth, 1 to 2 minutes. Season with hot sauce and salt, then transfer to a bowl.
Purée soup in 2 to 3 batches in cleaned blender until smooth (use caution when blending hot liquids), then strain through a fine-mesh sieve into a large bowl if desired. Reheat soup if necessary, then season with salt.
Serve soup drizzled with some red-pepper sauce and serve remaining sauce on the side or reserve for another use.