Creatures from the OSRIC core rules that originally appeared in the 1e Fiend Folio: Flind, Grimlock, Troll, Giant, Troll, Giant Two-Headed, Troll, Ice, Troll, Spectral, Coffer Corpse, Poltergeist, Bat, Mobat, Achaierai, Al-Mi'raj, Amber Creeping Vine (which is a name-variation of the OGC Yellow Musk Creeper), Babbler, Blindheim, Carbuncle, Caryatid Column, Caterwaul, Crabman, Crypt Thing, Dakon, Dark Creeper, Disenchanter, Ettercap, Mephit, Necrophidius, Nilbog, Skeleton Warrior, Stunjelly, Volt.
Creatures from the OSRIC core rules that originally appeared in the 1e Monster Manual 2: Quickling, Zombie, Juju, Annis, Aurumvorax, Barghest, Bee, Giant, Behir, Dracolisk, Executioner's Hood, Kraken, Mongrelman, Nereid, Phantom, Phoenix, Squealer, Vilstrak, Vulchling.
It's far from the complete list, of course. Some things are not OGC and not in the Tome of Horrors; some are too lame to include (I will never write up the flumph for OSRIC!); some I just couldn't cram into OSRIC's 400 pages and I'll release in future optional expansions (e.g. Azer); and some got completely replaced (e.g. the AD&D dinosaurs are based on science that was dodgy even in the 1970s, so I completely rewrote them for an audience that's seen Jurassic Park).