Cage housing of growing rabbits is associated with welfare concerns. An alternative system that has already been introduced involves pens with non-wire floors. An important aspect of group pens, for which the best solution has not yet been clearly demonstrated, is the choice of floor material. The study investigated effects of two ground floor types-slatted plastic floor versus concrete floor with straw litter-on health-related parameters and weight of rabbits reared in large group pens on a commercial rabbit farm, i.e., with preventive coccidiostatic, and if required, additional therapeutic medical treatment. Pens were identical in dimensions, equipment (including platforms), and initial group size (60 animals/pen). Four pens were studied per ground floor type in three consecutive rearing periods (in total, 12 pens per floor type). A higher percentage of rabbits per pen had clean fur if reared on straw ( p < 0.05). No significant differences were found in the load of coccidial oocysts in collective faecal samples, mortality, pathological alterations, or causes of loss ( p > 0.05). Thus, often-expressed concerns that parasitic load and mortality would be higher in groups kept on straw were not confirmed when rabbits were housed under otherwise equal conditions. Average slaughter weight was higher in rabbits reared on a slatted plastic floor ( p < 0.05), confirming previous findings of a negative impact of straw litter on weight gain.