Set oven rack about 6 inches from the heat source and preheat the oven's broiler. Arrange Anaheim chile peppers on a baking sheet.
Roast under the preheated broiler until chiles turn from bright green to dull green with some charred sections, about 5 minutes per side.
Transfer chiles to a resealable plastic bag; seal and steam peppers until skin loosens from pepper flesh, about 10 minutes. Carefully open the bag and pull charred skin from the chiles and scrape and remove the seeds. Slice chiles lengthwise and chop.
Mix chiles, avocados, tomatoes, onion, cilantro, lime juice, garlic, salt, and pepper together in a bowl, lightly mashing the avocados while stirring, until blended but before the avocados turn to mush.