This study reports on the effects of two rhizome-based establishment procedures ‘miscanthus under maize’ (MUM) and ‘reference’ (REF) on the methane yield per hectare (MYH) of miscanthus in a field trial in southwest Germany. The dry matter yield (DMY) of aboveground biomass was determined each year in autumn over four years (2016–2019). A biogas batch experiment and a fiber analysis were conducted using plant samples from 2016–2018. Overall, MUM outperformed REF due to a high MYH of maize in 2016 (7211 m3N CH4 ha−1). The MYH of miscanthus in MUM was significantly lower compared to REF in 2016 and 2017 due to a lower DMY. Earlier maturation of miscanthus in MUM caused higher ash and lignin contents compared with REF. However, the mean substrate-specific methane yield of miscanthus was similar across the treatments (281.2 and 276.2 lN kg−1 volatile solid−1). Non-significant differences in MYH 2018 (1624 and 1957 m3N CH4 ha−1) and in DMY 2019 (15.6 and 21.7 Mg ha−1) between MUM and REF indicate, that MUM recovered from biotic and abiotic stress during 2016. Consequently, MUM could be a promising approach to close the methane yield gap of miscanthus cultivation in the first year of establishment.