Paul Ellison and Gareth Roberts of KRE Corporate Recovery were appointed joint administrators of the company in the High Court on 17 November.
BigHospitality understands the group’s five sites remain open and no redundancies have been made while a buyer is being sought for the company's trade and assets on a going concern basis.
KRE has appointed independent valuers Lambert Smith Hampton to market the properties.
Grillstock began life as a barbecue and music festival in Bristol and opened a takeaway unit in the city in 2012, followed by its first permanent restaurant in 2013.
It also runs three other restaurants in London, Leicester and Bath with menus featuring pulled pork burgers, plates of mixed barbecued meat and a £6.95 Express lunch deal.
Grillstock has fallen in to administration at a time when the restaurant sector is struggling with a headwind of financial pressures, including rising food costs, business rates, and the introduction of the national living wage.