In the Generation I games there is unused Trainer data for Prof. Oak. This implies that the player was supposed to battle him at some point in the game.
In the data, Oak has level 66 Tauros, level 67 Exeggutor, level 68 Arcanine, level 70 Gyarados and one of the Kanto starters at level 69. This places his strength on-par with the player's rival and the Pokémon League Champion.
As well, four of his Pokémon are identical to the ones used by the Champion, only at higher levels, implying he was originally meant to be Champion, or at least another high-ranking Trainer.
The only way to fight him is through a glitch, you might want to find how to perform in on youtube!
