| Oasis Outsourcing Holdings, Inc. and Its AffiliatesWest Palm Beach, FL | 3 | 116,682 | Slavic401k |
| Oracle CorporationRedwood Shores, CA | 1 | 99,877 | Fidelity |
| O'Reilly Automotive, Inc.Springfield, MO | 1 | 93,644 | Fidelity |
| Ochsner Clinic FoundationNew Orleans, LA | 3 | 83,971 | Vanguard |
| Orlando Health, Inc.Orlando, FL | 3 | 70,304 | Fidelity |
| Oregon Retail Employees PensionTualatin, OR | 1 | 56,361 | Zenith American Solutions |
| OhiohealthColumbus, OH | 5 | 52,774 | Fidelity |
| Oak View Group, LLCPhiladelphia, PA | 2 | 51,703 | Fidelity |
| Omnicom Group Inc.New York, NY | 1 | 42,833 | Fidelity |
| Operating Engineers Pension TrustPasadena, CA | 1 | 40,018 | Platform IT Solutions |
| Ohio Carpenters' Pension PlanTroy, MI | 1 | 31,115 | Legacy Professionals LLP |
| Olin CorporationClayton, MO | 3 | 28,755 | Empower |
| Occidental Petroleum CorporationHouston, TX | 3 | 26,399 | n/a |
| Odp International, LLCBoca Raton, FL | 2 | 24,611 | Fidelity |
| Old Dominion Freight Line, Inc.Thomasville, NC | 1 | 23,909 | Empower |
| Operating Engineers Local 12Pasadena, CA | 1 | 23,643 | John Hancock |
| Oshkosh CorporationOshkosh, WI | 4 | 22,583 | Empower |
| Operating Engineers Local 324Troy, MI | 1 | 21,246 | Solxsys Administrative Solutions |
| Oncor Electric Delivery Company LLCDallas, TX | 2 | 21,230 | Fidelity |
| Operating Engineers Local 324, DCTroy, MI | 1 | 20,636 | Solxsys Administrative Solutions |
| Ohio Operating Engineers Pension PlanColumbus, OH | 1 | 20,036 | n/a |
| Owens CorningToledo, OH | 3 | 19,436 | Fidelity |
| Old Republic International Corp.Chicago, IL | 3 | 19,036 | Empower |
| Oak Street Health Mso, LLCChicago, IL | 2 | 17,805 | Fidelity |
| Omni Hotels Management CorporationDallas, TX | 1 | 17,413 | Empower |
| Owens & Minor, Inc.Glen Allen, VA | 2 | 17,272 | Fidelity |
| Ohio Carpenters' Annuity FundTroy, MI | 1 | 16,204 | John Hancock |
| O-I Glass, Inc.Perrysburg, OH | 6 | 16,090 | John Hancock |
| Onemain General Services CorporationEvansville, IN | 2 | 15,697 | Fidelity |
| Ohio Laborers Annuity FundWesterville, OH | 1 | 15,240 | Empower |
| Oak Crest Village, Inc.Cantonsville, MD | 2 | 13,949 | Principal |
| Operating Engineers Local #49 Defined Contribution PlanBloomington, MN | 1 | 12,571 | Milliman |
| Operating Engineers Local 825 Profit Sharing FundSpringfield, NJ | 1 | 12,327 | Empower |
| Office of the Commissioner of BaseballNew York, NY | 6 | 12,284 | Fidelity |
| Operating Engineers Local No. 825 Pension FundSpringfield, NJ | 1 | 11,674 | n/a |
| Officemax Inc., a Wholly Owned Subsidiary of the Odp CorporationBoca Raton, FL | 8 | 11,626 | n/a |
| Ou Medicine, Inc.Oklahoma City, OK | 1 | 11,359 | Fidelity |
| Onesmile, LLCCosta Mesa, CA | 1 | 9,768 | Fidelity |
| Option Care Health, Inc.Bannockburn, IL | 1 | 9,731 | Empower |
| Oneoncology, LLCNashville, TN | 2 | 9,710 | Sentinel |
| Open Text, Inc.Menlo Park, CA | 5 | 9,699 | Fidelity |
| Operating Engineers Local 428 Annuity Trust FundPhoenix, AZ | 2 | 9,580 | Southwest Service Administrators |
| Oper Eng. Loc 66 Annuity and Savings FundPittsburgh, PA | 1 | 9,294 | John Hancock |
| Outsource, LLCEl Segundo, CA | 1 | 8,620 | Fidelity |
| Oneok, Inc.Tulsa, OK | 3 | 8,573 | Fidelity |
| Olympus Corporation of the AmericasCenter Valley, PA | 2 | 8,503 | Empower |
| Oxford Industries, Inc.Atlanta, GA | 1 | 8,110 | Fidelity |
| Ohio Farmers Insurance CompanyWestfield Center, OH | 2 | 7,857 | T. Rowe Price |
| Ollie'S Bargain Outlet, Inc.Harrisburg, PA | 1 | 7,660 | Fidelity |
| Operating Engineers Local 101 Pension FundKansas City, MO | 1 | 7,502 | n/a |
| Oregon Processors Seasonal Employees Pension PlanPortland, OR | 1 | 7,327 | n/a |
| Owensboro Health, Inc.Owensboro, KY | 3 | 7,302 | Empower |
| One Gas, Inc.Tulsa, OK | 4 | 7,234 | Fidelity |
| Oldcastle Building Envelope, Inc.Dallas, TX | 5 | 7,000 | Fidelity |
| Oakmont Management Group LLCIrvine, CA | 1 | 6,921 | ADP |
| Oregon - Columbia Chapter AgcWilsonville, OR | 1 | 6,810 | Northwest Plan Services |
| Ohio State University Physicians, Inc.Columbus, OH | 2 | 6,734 | Nationwide |
| Orgill, Inc.Collierville, TN | 2 | 6,552 | Empower |
| Occidental Chemical CorporationHouston, TX | 4 | 6,446 | n/a |
| Oakwood Healthcare, Inc.Southfield, MI | 3 | 6,399 | n/a |
| Osi Restaurant Partners, LLCTampa, FL | 1 | 6,259 | Fidelity |
| Ogletree, Deakins, Nash, Smoak & StewartGreenville, SC | 3 | 6,063 | Fidelity |
| Otter Tail CorporationFargo, ND | 3 | 5,876 | Principal |
| Oge Energy Corp.Oklahoma City, OK | 2 | 5,671 | Fidelity |
| Okta, Inc.San Francisco, CA | 1 | 5,622 | Fidelity |
| Osram Sylvania Inc.Hillsboro, NH | 2 | 5,608 | n/a |
| Operating Engineers Local 77 Individual Account PlanSparks, MD | 1 | 5,491 | Empower |
| Overlake Hospital Medical CenterBellevue, WA | 3 | 5,420 | Fidelity |
| Old National BancorpEvansville, IN | 6 | 5,293 | Empower |
| Oceaneering International, Inc.Houston, TX | 1 | 5,250 | Fidelity |
| Otis Worldwide CorporationFarmington, CT | 2 | 5,192 | Alight |
| Openlane, Inc.Carmel, IN | 1 | 5,109 | Fidelity |
| Octapharma Plasma, Inc.Charlotte, NC | 1 | 5,084 | Principal |
| Onex TSG Intermediate Corp.Lafayette, LA | 1 | 5,030 | Empower |
| Osmose Utilities Services, Inc.Peachtree City, GA | 1 | 5,001 | Fidelity |
| Overhead Door CorporationLewisville, TX | 3 | 4,829 | Empower |
| -Oregon Laborers- Employers Pension Trust FundPortland, OR | 1 | 4,811 | Milliman |
| Orange County Ibew-Neca ElectricalSan Jose, CA | 1 | 4,741 | Empower |
| Okonite Company IncRamsey, NJ | 6 | 4,671 | Transamerica |
| Ocean Spray Cranberries, Inc.Lakeville-Middleboro, MA | 4 | 4,655 | Fidelity |
| Oneblood, Inc.ST. Petersburg, FL | 3 | 4,223 | n/a |
| Operative Plasterers and Cement MasonsCanfield, OH | 1 | 4,220 | Benesys |
| Ohio LivingWesterville, OH | 1 | 4,129 | Voya |
| O'Neal Steel, Inc.Birmingham, AL | 2 | 3,863 | Fidelity |
| Opko Health, Inc.Miami, FL | 1 | 3,727 | Fidelity |
| Otb Acquisition LLCIrving, TX | 1 | 3,174 | Economic Group Pension Services |
| Oregon Tool, Inc.Portland, OR | 2 | 2,762 | Fidelity |
| Oil States International, Inc.Houston, TX | 1 | 2,704 | Fidelity |
| The Ogilvy Group, LLCNew York, NY | 4 | 2,229 | Mercer |
| Organon LLCJersey City, NJ | 3 | 2,033 | Fidelity |
| Optumcare Management, LLCMinnetonka, MN. No active plan; last report 2022 | 1 | 19,848 | n/a |
| Omnicare, Inc.Cincinnati, OH. No active plan; last report 2014 | 2 | 19,652 | n/a |
| Oregon SW Washington CarpentersSeattle, WA. No active plan; last report 2021 | 1 | 16,171 | n/a |
| OPTUM360 Services, Inc.Minnetonka, MN. No active plan; last report 2021 | 1 | 9,257 | n/a |
| Outboard MarineWaukegan, IL. Pension taken over by the PBGC | 1 | 8,894 | n/a |
| Ormet Primary Aluminum CorporationHannibal, OH. No active plan; last report 2014 | 3 | 7,439 | n/a |
| Ohio and Vicinity Regional CouncilAustintown, OH. No active plan; last report 2015 | 1 | 7,433 | n/a |
| Odyssey Healthcare Management, L.P.Atlanta, GA. No active plan; last report 2011 | 1 | 7,121 | n/a |
| Operating Engineers Local 428 Annuity Trust FundPhoenix, AZ. No active plan; last report 2016 | 1 | 6,337 | n/a |
| Olan Mills, Inc.Chattanooga, TN. No active plan; last report 2013 | 2 | 6,310 | n/a |
| Oldcastle Architectural, Inc.Atlanta, GA. No active plan; last report 2012 | 1 | 5,996 | n/a |
| Orchard Supply Company LLCMooresville, NC. No active plan; last report 2021 | 1 | 5,423 | n/a |
| Optumrx Administrative Services, LLCMinnetonka, MN. No active plan; last report 2017 | 1 | 5,345 | n/a |