Pretty self explanatory. Like the Hong Kong dubs, the studios aren't credited, so one shouldn't assume all of these were done by Frontier.

Toho films 

-The Last Gunfight (1960)

-The Last War (1961)

-The Merciless Trap (1961; "Dubbing by EIKOSHA, TOKYO")

-Attack Squadron! (1963)

-High and Low (1963)

-Ebirah Horror of the Deep (1966)

-Son of Godzilla (1967)

-Destroy All Monsters (1968)

-Admiral Yamamoto (1968)

-Battle of the Japan Sea (1969)

-Princess from the Moon (1987) 

Unconfirmed 

-Varan (1958)

-The Weed of Crime (1962) -  The international trailer was definitely dubbed in Tokyo. 

-King Kong vs. Godzilla (1962) - The international trailer was definitely dubbed in Tokyo. Apparently only the trailer was dubbed in Tokyo and a full length dub made elsewhere may exist.

-King Kong Escapes (1967)

-Booted Babe, Busted Boss (1968) - The international trailer was definitely dubbed in Tokyo. 

-Vampire Doll (1970)

-Submersion of Japan (1973)

Other studios

-The Warped Ones (Nikkatsu) (1960; Unconfirmed) Released in the US as The Weird Lovemakers.

-The Little Prince and the Eight-Headed Dragon (Toei) (1963; United Service, Inc.)

-Gappa, the Triphibian Monster (Nikkatsu) (1967)

-Watari the Conqueror (Toei) (ca. 1967; Pedro Production, Ltd.) (Not credited)

-Watari and the Fantasticks (Toei) (ca. 1967; Pedro Production, Ltd.) (Not credited)

-The Green Slime (Toei) (1968) *

-Gamera vs. Guiron (Daiei) (1969; Pedro Production, Ltd.) (Not credited)**

-The Falcon Fighters (Daiei) (1969; Pedro Production, Ltd.)

-The Bullet Train (Toei) (1975)

-The Legend of Dinosaurs and Monster Birds (Toei) (1977)

-Samurai Reincarnation (Toei) (1981)

-Ninja Wars (Toei) (1982)

* A good deal of characters' voices were post-dubbed. Frontier regular Burr Middleton can be heard all over the film.

** Pedro Production might or might not have been located in Japan. Pedro Komiyama is credited as the dubbing director of THE FALCON FIGHTERS. IMDb says a Pedro Komiyama (probably the same one) appeared in the 1959 Shochiku film NIKAIDOU TAKUYA - GINZA BURAICHOU: GINZA MITE GUY. It's also uncertain if Pedro Production was responsible for the GUIRON dub; the presence of several voice actors from THE FALCON FIGHTERS and the same inane scripting are the only pieces of evidence.