The list of standard abbreviations for JDS is available at adsa.org/jds-abbreviations-24. Nonstandard abbreviations are available in the Notes. International trends of increasing dairy herd sizes coupled with scarcity of labor have necessitated the enhancement of labor efficiency for dairy production systems. This study quantified the effects of infrastructure, automation, and management practices on the milking and operator efficiency of herringbone and rotary parlors used on pasture-based farms in Ireland. Data were used from 592 milkings across 26 farms (16 herringbones and 10 rotaries). The metrics of cows milked per hour (cows/h), cows milked per operator per hour (cows/h per operator), and liters of milk harvested per hour (L/h) described milking efficiency. The metrics of total process time per cow (TPT, s/cow), milk process time per cow (MPT, s/cow), work routine time (WRT, s/cow), cluster time (CT, s/cluster), and attachment time per cow (ATC, s/cow) described operator efficiency. Automations investigated were backing gates, cluster flush, plant wash, cluster removers (ACR), feeders, entry gates, rapid exit, and teat spray. Additional operator presence at milking was also investigated. Herringbone and rotary parlors were assigned to quartiles from their cows/h per operator values to examine variations in infrastructure, automations, and management practices. Fourth quartile (Q4) herringbones based on cows/h per operator values averaged 93 cows/h per operator using average system sizes of 24 clusters with 5 parlor automations. The Q4 rotaries averaged 164 cows/h per operator using average system sizes of 47 clusters and an average CT of 13 s/cluster. Cows/h per operator values for Q4 herringbone and rotary parlors were 82% and 54% higher, respectively, than values observed on first quartile parlors, indicating the considerable potential to improve efficiency. To determine if infrastructure, automations, or additional operators at milking significantly affected operator efficiencies, general linear mixed models were developed. For parlor infrastructure, additional clusters had greater significance on operator efficiencies (MPT) for herringbones (−1.3 s/cow) as opposed to rotaries (−0.2 s/cow). Hence, increases in system size were likely to result in improved efficiencies for herringbones but less so for rotaries. For automations, ACR significantly reduced herringbone TPT, CT, and WRT values by 13.3 s/cow, 18.9 s/cluster, and 32.6 s/cow, respectively, whereas rapid exit significantly lowered CT by 18.6 s/cluster. We found no significant effect on rotary TPT, MPT, CT, or WRT values from the use of automatic teat sprayers. An additional operator at milking was found to significantly reduce herringbone TPT but not MPT or CT. For rotaries, a second operator had no significant effect on TPT, MPT, CT, or WRT values. We documented strong negative correlations between operator efficiencies (TPT, MPT) and milking efficiency (cows/h) for both herringbone (−0.91, −0.84) and rotaries (−0.98, −0.89). Strong negative correlations between the herringbone automation count and TPT (−0.80), MPT (−0.72), and CT (−0.75) suggested highly automated parlors were likely to achieve greater operator efficiencies than less automated parlors. The strong negative correlation (−0.81) between rotary milking efficiency (cows/h) and CT suggested that lower CT values (i.e., rotation speed) resulted in increased milking efficiency. Overall, our study quantified the effects of parlor infrastructure, automation, and management practices on the milking and operator efficiency of herringbone and rotary parlors. [ABSTRACT FROM AUTHOR]