We're in Lunatic Crystal's postgame! Technically Professor Oak can be battled after defeating Blue, but I left him for now since he is Level 100 just like the Final Rival and Red.
Professor Oak's team:
- Tauros (Pink Bow): Return, Megahorn, Earthquake, Hidden Power Flying
- Dragonite (Pink Bow): Thunder Wave, Outrage, Extremespeed, Hidden Power Flying
- Blastoise (Leftovers): Toxic, Protect, Surf, Ice Beam
- Venusaur (Miracle Seed): Giga Drain, Earthquake, Sludge Bomb, Sleep Powder
- Charizard (Charcoal): Outrage, Sky Attack, Flamethrower, Solarbeam
- Mew (Miracleberry): Swords Dance, Psychic, Fire Blast, Submission
The three Kanto starters and Tauros are references to his unused team in Generation 1, Dragonite is there since he has one in the anime and Mew is a reference to Pokemon Masters.
After Professor Oak is defeated he can still be battle any time you want by talking to him again and you will get the same dialouge. If you decline Oak's offer to battle he will check your Pokedex as usual.