X0306 4 2021-10-15 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 2021-10-15 4 S 0 10353 61.67 D 1346430 D Common Stock 2021-10-15 4 S 0 20029 62.44 D 1326401 D Common Stock 2021-10-15 4 S 0 820 63.42 D 1325581 D Common Stock 2021-10-15 4 S 0 500 64.22 D 1325081 D Common Stock 2021-10-18 4 S 0 37826 64.08 D 1287255 D Common Stock 2021-10-18 4 S 0 15357 63.10 D 1271898 D Common Stock 2021-10-18 4 S 0 200 62.15 D 1271698 D Common Stock 2021-10-19 4 S 0 13234 60.96 D 1258464 D Common Stock 2021-10-19 4 S 0 1581 61.61 D 1256883 D Common Stock 2021-10-19 4 S 0 100 62.62 D 1256783 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 $61.08 to $62.07, 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 $62.08 to $63.02, 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 $63.13 to $63.77, 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 $63.56 to $64.55, 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 $62.63 to $63.55, 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 $60.48 to $61.45, 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 $61.48 to $62.00, 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 transactions reported in this Form 4 were effected pursuant to a Rule 10b5-1 Trading Plan adopted by the Reporting Person. /s/ Nasym Afsari, Attorney in fact 2021-10-19