| Operation Desert Storm target | 29 |
| Operation Enduring Care gp. | 27 |
| Operation Exodus participant | 28 |
| Operation Hastings org. | 23 |
| Operation IceBridge grp. | 24 |
| Operation in 1998 news | 22 |
| Operation Just Cause target | 27 |
| Operation Mail Call gp. | 23 |
| Operation Mail Call grp. | 24 |
| Operation Neptune Spear org. | 28 |
| Operation Overlord beach | 24 |
| Operation Overlord high point | 29 |
| Operation Overlord launch | 25 |
| Operation Overlord monogram | 27 |
| Operation Overlord overseer | 27 |
| Operation Overlord site | 23 |
| Operation Overlord time | 23 |
| Operation Overlord's time | 29 |
| Operation Overlord, e.g. | 24 |
| Operation Phone Home gp. | 24 |
| Operation Pipe Dreams org. | 26 |
| Operation Red Dawn city | 23 |
| Operation Redwing event, 1956 | 29 |
| Operation since August 1990 | 27 |
| Operation Solomon airline | 25 |
| Operation Trinity event | 23 |
| Operation Trinity locale | 24 |
| Operation ___ Freedom (2003) | 28 |
| Operation-launching times | 25 |
| Operational headquarters | 24 |
| Operative's employer | 24 |
| Operator of a metal plant | 25 |
| Operator of MouthHealthy.org | 28 |
| Operator's accessory | 24 |
| Operator's concern: Abbr. | 29 |
| Operator's number? | 22 |
| Operator's post, once | 25 |
| Operator's request | 22 |
| Operator's request? | 23 |
| Operators standing by? | 22 |
| Operetta composer Franz | 23 |
| Operetta princess and others | 28 |
| Operetta set in Titipu | 22 |
| Ophelia and Hamlet, e.g. | 24 |
| Ophelia or Claudius, e.g. | 25 |
| Ophelia or Laertes, e.g. | 24 |
| Ophelia's thought flower | 28 |
| Ophiologist's study | 23 |
| Ophthalmic concern (Var.) | 25 |
| Ophthalmic development | 22 |
| Ophthalmologic concern | 22 |
| Ophthalmologic problem | 22 |
| Ophthalmological concern | 24 |
| Ophthalmological study | 22 |
| Ophthalmologist's case | 26 |
| Ophthalmologist's cases | 27 |
| Ophthalmologist's concern | 29 |
| Ophthalmologist's office? | 29 |
| Ophthalmologist's order | 27 |
| Ophthalmologist's study | 27 |
| Ophthalmologist's supply | 28 |
| Ophthalmologist's tool | 26 |
| Opie Taylor's caretaker | 27 |
| Opie's answer to Aunt Bee | 29 |
| Opie, at the lake, sometimes | 28 |
| Opine, with "in" | 26 |
| Opinion column, briefly | 23 |
| Opinion of Keats poetry? | 24 |
| Opinion page perspective | 24 |
| Opinion piece by a sot? | 23 |
| Opinion piece, for short | 24 |
| Opinion piece, in Nice | 22 |
| Opinion sharer's remark | 27 |
| Opinion, after deflation? | 25 |
| Opinion, forward or backward | 28 |
| Opinions from a coward? | 23 |
| Opium poppies have them | 23 |
| Opium-derived analgesic | 23 |
| Opossum's branch grabber | 28 |
| Opp. of "take out" | 28 |
| Opp. of legato, in music | 24 |
| Oppenheimer development | 23 |
| Oppenheimer opposed it | 22 |
| Oppenheimer's agcy. | 23 |
| Oppenheimer's alma mater | 28 |
| Opponent for Bjorn or Vitas | 27 |
| Opponent for Juan Belmonte | 26 |
| Opponent for Minnesota Fats | 27 |
| Opponent in an argument | 23 |
| Opponent of George and Bill | 27 |
| Opponent of government | 22 |
| Opponent of Jimmy and Arthur | 28 |
| Opponent of Muhammad: 1978 | 26 |
| Opponent of the CAN-SPAM act | 28 |
| Opponent of U. S. Grant | 23 |
| Opponent's utterance | 24 |
| Opponents of 'us' | 25 |
| Opponents of "us" | 27 |
| Opportunist with tickets | 24 |
| Opportunities at home? | 22 |