Parents of autistic children experience elevated stress relative to parents of children with neurotypical development and children with other intellectual and developmental disabilities. Adverse effects of parenting stress on parent, child, and family functioning may be especially heightened for marginalized families. We conducted a randomized controlled trial that demonstrated the efficacy of Mindfulness Based Stress Reduction (MBSR) relative to psychoeducational support (PE) for reducing stress in diverse and underserved parents of autistic preschoolers. This paper presents implementation data, and examines efficacy across in-person and virtual intervention modalities. (author abstract)