Exhibit 99 Form 4 Joint Filer Information Name: EnCap Energy Capital Fund VIII Co-Investors, L.P. Address: 1100 LOUISIANA STREET, SUITE 4900 HOUSTON, TX 77002 Issuer & Ticket Symbol: Montage Resources Corporation [MR] Date of Event Requiring Statement: 11/13/2020 Relationship of Reporting Person 10% Owner to Issuer: Signature: EnCap Energy Capital Fund VIII Co-Investors, L.P. By: EnCap Equity Fund VIII GP, L.P., its general partner By: EnCap Investments L.P., its general partner By: EnCap Investments GP, L.L.C, its general partner By: /s/ Douglas E. Swanson, Jr., ------------------------------- Managing Director Date: 11/13/2020 Name: EnCap Energy Capital Fund IX, L.P. Address: 1100 LOUISIANA STREET, SUITE 4900 HOUSTON, TX 77002 Issuer & Ticket Symbol: Montage Resources Corporation [MR] Date of Event Requiring Statement: 11/13/2020 Relationship of Reporting Person 10% Owner to Issuer: Signature: EnCap Energy Capital Fund IX, L.P. By: EnCap Equity Fund IX GP, L.P., its general partner By: EnCap Investments L.P., its general partner By: EnCap Investments GP, L.L.C, its general partner By: /s/ Douglas E. Swanson, Jr., ------------------------------- Managing Director Date: 11/13/2020 Name: EnCap Partners GP, LLC Address: 1100 LOUISIANA STREET, SUITE 4900 HOUSTON, TX 77002 Issuer & Ticket Symbol: Montage Resources Corporation [MR] Date of Event Requiring Statement: 11/13/2020 Relationship of Reporting Person 10% Owner to Issuer: Signature: By: /s/ Douglas E. Swanson, Jr., ------------------------------- Managing Director Date: 11/13/2020 Name: TPR Residual Assets, LLC Address: 1100 LOUISIANA STREET, SUITE 4900 HOUSTON, TX 77002 Issuer & Ticket Symbol: Montage Resources Corporation [MR] Date of Event Requiring Statement: 11/13/2020 Relationship of Reporting Person 10% Owner Signature: TPR Residual Assets, LLC By: Excalibur Resources Holdings, LLC, its sole member By: EnCap Energy Capital Fund IX, L.P., its sole member By: EnCap Equity Fund IX GP, L.P., its general partner By: EnCap Investments L.P. its general partner By: EnCap Investments GP, L.L.C., its general partner Signature: By: /s/ Douglas E. Swanson, Jr., ------------------------------- Managing Director Date: 11/13/2020