X0306 4 2021-09-10 0 0001643615 Montrose Environmental Group, Inc. MEG 0001079972 PERLMAN RICHARD E 1 PARK PLAZA, SUITE 1000 IRVINE CA 92614 1 0 0 0 Common Stock 2021-09-10 4 S 0 37584 57.37 D 1383874 D Common Stock 2021-09-10 4 S 0 27091 57.95 D 1356783 D Common Stock 2020-09-13 4 S 0 18260 57.08 D 1338523 D Common Stock 2020-09-13 4 S 0 17065 57.59 D 1321458 D The price reported in Column 4 is a weighted average price. These shares of common stock of the Issuer were sold in multiple transactions by the Reporting Person at prices ranging from $56.65 to $57.63, inclusive. The Reporting Person undertakes to provide upon request by the Commission staff, the Issuer, or a security holder of the Issuer full information regarding the number of shares of common stock sold at each separate price within the range. The price reported in Column 4 is a weighted average price. These shares of common stock of the Issuer were sold in multiple transactions by the Reporting Person at prices ranging from $57.68 to $58.29, inclusive. The Reporting Person undertakes to provide upon request by the Commission staff, the Issuer, or a security holder of the Issuer full information regarding the number of shares of common stock sold at each separate price within the range. The price reported in Column 4 is a weighted average price. These shares of common stock of the Issuer were sold in multiple transactions by the Reporting Person at prices ranging from $56.39 to $57.37, inclusive. The Reporting Person undertakes to provide upon request by the Commission staff, the Issuer, or a security holder of the Issuer full information regarding the number of shares of common stock sold at each separate price within the range. The price reported in Column 4 is a weighted average price. These shares of common stock of the Issuer were sold in multiple transactions by the Reporting Person at prices ranging from $57.39 to $58.06, inclusive. The Reporting Person undertakes to provide upon request by the Commission staff, the Issuer, or a security holder of the Issuer full information regarding the number of shares of common stock sold at each separate price within the range. /s/ Nasym Afsari, Attorney in fact 2021-09-13