1 Syllable: S
Ian, leant
2 Syllables: SU
beacon, beaming, beaten, beating, being, bleaching, bleating, bleeding, breathing, breeding, ceasing, ceding, ceiling, cheating, cheering, chieftain, cleaning, clearance, clearing, cleaving, Cleveland, creaking, credence, creeping, deacon, dealing, decent, deeming, deepen, demon, deviant, dreaming, earrings, easing, Eastman, Easton, eaten, eating, Eaton, Eden, Ephraim, Eton, even, evening, fearing, feasting, feeding, feeling, ference, Fielding, fleeing, fleeting, Freedman, freedmen, freedom, freeing, Freeman, Freeman's, freezing, frequent, Friedman, gearing, gleaming, gleanings, Grecian, Greenland, greeting, grievance, grieving, healing, heaping, hearing, heathen, heating, heaving, heeding, helium, jeering, keeping, kneeling, leading, leaking, leaning, leaping, leasing, leaving, legion, Leland, lenient, lesion, meaning, median, medium, meeting, Museum, nearing, needing, peeling, peeping, peering, Pekin, piquant, pleading, pleasing, preaching, precinct, premium, prescience, reaching, reading, reagent, realism, reaping, rearing, reason, recent, reeking, reeling, refund, Regent, region, scheming, screaming, screeching, screening, sealing, seaman, seamen, season, seating, seeding, seedlings, seeing, seeking, seeming, seething, seizing, semen, sequence, serum, shearing, sheepskin, shielding, shrieking, sleeping, sneaking, sneering, sneezing, speaking, speeding, squeaking, squeezing, stealing, steaming, steering, Stephen, Steven, streaming, Sweden, sweeping, sweeten, syringe, teaching, tearing, teasing, tedium, teeming, theorem, thieving, treason, treating, treatment, weaken, weaning, weaving, weeding, weekend, weeping, wheeling, wielding, yielding, Zealand
2 Syllables: US
Bodleian, Crimean, Korean, Lyceum, plebeian
3 Syllables: SUU
3 Syllables: USU
3 Syllables: UUS
4 Syllables: UUSU
4 Syllables: UUUS
5 Syllables: UUUSU

Found 320 words across 9 groupings. Skipped 64 excess words of a similar stem.