montrose environmental group, inc. is a national, high-growth environmental company offering air quality, environmental laboratory, and regulatory compliance services to a diverse range of clients in industry and government. montrose operates under a variety of different brands across the country. each brand is well-established and represents a long tradition of delivering high-quality environmental services to our clients. headquartered in orange county, california, montrose environmental group, inc. has 42+ offices and 750+ employees nationwide.