We consider a vertically related market where an upstream monopolist supplier trades, via interim observable two-part tariff contracts, with two differentiated downstream Cournot competitors. We show that passive partial backward ownership (PPBO) is pro-competitive and welfare enhancing. PPBO exacerbates the upstream monopolist's commitment problem and yields lower wholesale prices, and higher industry output, consumers surplus, and welfare than in the absence of PPBO. (C) 2022 Elsevier B.V. All rights reserved.