Ordinarily I wouldn't have mentioned either of these guys, but when one gets to the letter Q, the pickings are desperately slim!
Quantz (Johann Joachim) was an 18th-century flautist and composer specializing in, natch, flute music. He served Prussia's King Frederick II, who was himself a flute-player and composer (King Fritz even wrote four symphonies!). Quantz himself wrote some 300 flute concertos, but he is mainly remembered as an authority on the flute technique of his time.
Quilter (Roger) was an early-20th-century British composer, best remembered for his art songs based on Elizabethan and Jacobean lyrics. He also wrote A Children's Overture, based on nursery rhymes, an opera titled Love at the Inn, and incidental music for a play, Where the Rainbow Ends.