ASU and Southwest Autism Resource and Research Center will be responsible for all recruitment procedures.  All recruitment tools are approved by ASU, the IRB of record.  Because of the team's previous research on adults with autism, there is a large recruitment pool and the tools and reputation in the community to recruit successfully within the Phoenix area. The team has now successfully recruited over 200 adults with ASD, which continues to grow, in the ASU ASD research program. Our partners at SARRC have a recruitment database of hundreds of additional eligible adults aged 21 years and older, a much larger population than our prior studies restricted to older adults. We have frequent interactions with support companions (parents and spouses and, occasionally, friends). Eligible participants in these two databases will be contacted by a member of the research team via telephone or email. The researcher will use the recruitment and screening script (described below and attached) to determine whether the participant is interested and eligible to participate in the study. Interested individuals who complete this online survey or contact the ASU Autism Brain and Aging (ABA) Laboratory will be contacted via telephone. The recruitment and screening script (attached) will be used to obtain verbal consent prior to confirming survey responses or asking questions assessing eligibility, including diagnosis. The phone screen will also include the Wide Range Achievement Test (WRAT) to obtain an estimated IQ score to estimate eligibility. The WRAT takes about 5 minutes to complete and requires the participant to read a list of words over the phone. This list of words will be emailed to the participant along with a standard, approved email template (attached). Interested individuals who meet the preliminary eligibility criteria during the phone screen will be scheduled for a visit at SARRC to formally assess their ASD diagnosis and IQ. If individuals have completed these procedures at SARRC within the last ten years, they will not be re-assessed for ASD diagnosis and IQ.

Inclusion Criteria:

• Age 21 to 70 years old
• ASD diagnosis via gold-standard diagnostic assessments (Autism Diagnostic Observation Schedule-2)
• Must have a support companion (e.g., parent, spouse, sibling, friend) willing and able to participate in the intervention
• Must be willing to be randomized to a treatment or delayed treatment control group
• Must be able to attend at least 14 of the 16 intervention sessions if assigned to PEERS group, or 28 of the 32 intervention sessions if assigned to PEERS-plus group
• English speaking: Participants must be English-speaking because the screening and behavioral measures are in English (including the intelligence estimate), as well as the intervention content

Exclusion Criteria:

• Non-verbal participants will be excluded to ensure test compliance and increase sample homogeneity.
• Participants with IQ scores <70 will be excluded because the interventions were developed for individuals without intellectual disability. We will screen participants for this inclusion criteria with the Wide Range Achievement Test during the phone screen.