| OneAmericaEIN 20-0384893 | Human and Civil Rights | WA | $3,534,222Mid-sized | 88.68 |
| OneFamilyEIN 11-3585917 | Human Services | NJ | $1,086,033Small | 82.43 |
| OneGoalEIN 56-2369898 | Education | IL | $11,929,410Mid-sized | 85.76 |
| OneSightEIN 31-1385607 | International | OH | $19,899,787Large | 92.61 |
| OneSkyEIN 95-4714047 | International | CA | $6,328,760Mid-sized | 92.63 |
| OneVoice MovementEIN 30-0102398 | International | NY | $3,731,582Mid-sized | 88.81 |
| Open Air Campaigners-USAEIN 36-2420024 | Religion | PA | $1,402,536Small | 78.77 |
| Open Arms of MinnesotaEIN 41-1681317 | Human Services | MN | $3,381,410Small | 91.45 |
| Open BooksEIN 20-4830666 | Education | IL | $2,045,810Small | 84.17 |
| Open Door Community HouseEIN 58-0601980 | Human Services | GA | $1,511,733Small | 92.44 |
| Open Door MinistriesEIN 56-1576543 | Human Services | NC | $1,696,558Small | 74.89 |
| Open Door Mission, HoustonEIN 76-0146890 | Human Services | TX | $2,973,113Small | 80.91 |
| Open Door Mission, OmahaEIN 47-0411375 | Human Services | NE | $29,651,669Large | 89.84 |
| Open Doors KalamazooEIN 23-7088427 | Human Services | MI | $1,150,677Small | 94.14 |
| Open Doors USAEIN 23-7275342 | Religion | CA | $23,492,166Large | 87.35 |
| Open HandEIN 58-1816778 | Human Services | GA | $11,503,460Mid-sized | 88.63 |
| Open SchoolEIN 93-0757378 | Education | OR | $5,210,734Mid-sized | 91.78 |
| Open Your Heart to the Hungry and HomelessEIN 36-3488089 | Human Services | MN | $784,716Small | 89.50 |
| OpenhouseEIN 94-3337955 | Human Services | CA | $1,606,068Small | 89.17 |
| OPERA AmericaEIN 20-3520577 | Arts, Culture, Humanities | NY | $7,895,530Mid-sized | 91.83 |
| Opera ColoradoEIN 84-0850527 | Arts, Culture, Humanities | CO | $4,098,622Mid-sized | 74.02 |
| Opera Company of PhiladelphiaEIN 23-1504706 | Arts, Culture, Humanities | PA | $14,101,013Large | 78.76 |
| Opera MemphisEIN 62-0785544 | Arts, Culture, Humanities | TN | $1,623,169Small | 83.52 |
| Opera OmahaEIN 47-6032795 | Arts, Culture, Humanities | NE | $3,861,688Mid-sized | 96.90 |
| Opera San JoséEIN 77-0009773 | Arts, Culture, Humanities | CA | $4,434,463Mid-sized | 92.72 |
| Opera Theatre of Saint LouisEIN 43-0821958 | Arts, Culture, Humanities | MO | $10,222,016Mid-sized | 93.44 |
| Operation AccessEIN 94-3180356 | Health | CA | $1,466,203Small | 86.33 |
| Operation Blessing InternationalEIN 54-1382657 | International | VA | $272,605,727Large | 82.43 |
| Operation Bootstrap AfricaEIN 41-6051952 | International | MN | $838,344Small | 95.15 |
| Operation BreakthroughEIN 43-0971560 | Human Services | MO | $8,616,112Mid-sized | 95.72 |
| Operation Finally HomeEIN 20-8964096 | Human Services | TX | $6,922,291Mid-sized | 80.85 |
| Operation First ResponseEIN 20-1622436 | Human Services | VA | $803,443Small | 91.16 |
| Operation Food SearchEIN 43-1241854 | Human Services | MO | $33,636,061Large | 94.03 |
| Operation FuelEIN 06-1253091 | Human Services | CT | $4,590,024Mid-sized | 92.66 |
| Operation GratitudeEIN 20-0103575 | Human Services | CA | $10,112,056Mid-sized | 92.38 |
| Operation HomefrontEIN 32-0033325 | Human Services | TX | $48,352,893Large | 89.18 |
| Operation HOPEEIN 95-4378084 | Education | CA | $15,027,756Large | 87.82 |
| Operation KindnessEIN 75-1553350 | Animals | TX | $4,625,577Mid-sized | 90.01 |
| Operation NightwatchEIN 91-0964027 | Human Services | WA | $1,154,918Small | 87.82 |
| Operation Second ChanceEIN 20-2624345 | Human Services | MD | $1,112,969Small | 91.85 |
| Operation ShoestringEIN 64-0471554 | Human Services | MS | $1,215,347Small | 93.27 |
| Operation USAEIN 95-3504080 | International | CA | $3,338,684Small | 92.92 |
| Opportunity Fund Community Development EIN 31-1719434 | Community Development | CA | $19,078,312Large | 91.49 |
| Opportunity, Inc. of Palm Beach CountyEIN 59-0624429 | Education | FL | $1,751,901Small | 94.06 |
| Optimist International FoundationEIN 23-7102928 | Education | MO | $1,513,808Small | 90.41 |
| Oral Roberts Evangelistic AssociationEIN 73-0568096 | Religion | OK | $7,500,362Mid-sized | 68.46 |
| Orange County CoastkeeperEIN 33-0847892 | Environment | CA | $1,772,988Small | 94.74 |
| Orange County Community FoundationEIN 33-0378778 | Community Development | CA | $64,365,979Large | 94.37 |
| Orange County Museum of ArtEIN 95-1660847 | Arts, Culture, Humanities | CA | $2,605,178Small | 85.08 |
| Orange County Rescue MissionEIN 95-2479552 | Human Services | CA | $16,241,092Large | 91.21 |
| Orange County United WayEIN 33-0047994 | Community Development | CA | $17,947,341Large | 89.73 |
| Orangewood FoundationEIN 95-3616628 | Human Services | CA | $9,272,668Mid-sized | 92.50 |
| Orangutan Foundation InternationalEIN 95-4112467 | Animals | CA | $1,603,050Small | 93.42 |
| Orbis InternationalEIN 23-7297651 | International | NY | $209,113,219Large | 95.47 |
| Orchestra of St. Luke'sEIN 51-0201839 | Arts, Culture, Humanities | NY | $7,749,571Mid-sized | 86.11 |
| Ordway Center for the Performing ArtsEIN 41-1428998 | Arts, Culture, Humanities | MN | $21,131,100Large | 91.33 |
| Oregon Ballet TheatreEIN 93-1009305 | Arts, Culture, Humanities | OR | $7,234,406Mid-sized | 90.58 |
| Oregon Energy FundEIN 93-1029893 | Human Services | OR | $1,245,206Small | 89.18 |
| Oregon Food BankEIN 93-0785786 | Human Services | OR | $67,194,439Large | 90.96 |
| Oregon Health & Science University FoundationEIN 23-7083114 | Education | OR | $130,218,507Large | 91.70 |