Place chopped tomatillos in strainer set over large bowl and let drain 1 hour. Discard juices in bowl. Transfer tomatillos to large serving bowl. Add avocados, red onion, cilantro, lime juice, olive oil, and chiles; stir gently to mix. Season salsa to taste with salt. DO AHEAD: Can be made 2 hours ahead. Cover and refrigerate.
Serve salsa with tortilla chips.
Green, tomato-like fruits with papery husks; available in the produce section of some supermarkets and at Latin markets.