To further evaluate, using quasi-experimental methodologies, posthospital brain injury rehabilitation outcomes described in an accompanying report of a large observational study (n =2120). Data from Intensive Rehabilitation (IR: Residential Neurobehavioral, Residential Neurorehabilitation, Home and Community Neurorehabilitation, Day Treatment, Outpatient Neurorehabilitation) and Supported Living (SL) programs serving individuals with acquired brain injury (ABI). Two hundred twenty-eight individuals with traumatic brain injury, stroke, or other ABI in propensity score analysis; 1344 in analysis by extent of recommended treatment completed (TC) rating. Sex, age, time since injury, Mayo-Portland Adaptability Inventory-4th edition (MPAI-4) Rasch-derived T-scores, and TC rating. Analyses of covariance (1) of discharge MPAI-4 Total, index, and subscale T-scores on propensity score-matched samples of IR and SL participants controlling for admission scores and (2) of MPAI-4 T-scores by TC rating and diagnostic category. Propensity score-matched groups showed superior outcomes for IR participants compared to SL participants on MPAI-4 Total T-score (F =77.21, P <.001; partial η2=0.257) and all MPAI-4 index and subscale T-scores controlling for sex, age, and baseline scores. Participants with traumatic brain injury and stroke who completed the recommended course of rehabilitation had superior outcomes on all MPAI-4 T-scores compared to those who completed less than or much less than the recommended treatment. No additional benefit was apparent for those who completed more than the recommended course. The association between TC rating and outcome was not significant for the other ABI group. These analyses using quasi-experimental controls provide more scientifically rigorous evidence of the benefit of IR provided through posthospital brain injury rehabilitation programs after acute inpatient care, consistent with the results of numerous observational studies. However, improved internal validity limits external validity and generalization. The absence of a significant association between TC rating and outcomes for the other ABI group most likely reflects the difficulty prescribing rehabilitation for this highly heterogeneous group.