麻油Q米血 on a menu in Taipei
Q is Chinese slang for "chewy", similar to al dente in texture. You can see it in example phrases such as "Q感十足" (very chewy). You would expect foods such as tapioca pearls, gelatinous candies, pasta, or rice to be described as "Q".

From my experience, this term is more popular in Taiwan and Hong Kong and less so in the mainland. I have not seen this term in the 90's or before.

I'm not sure where this phrase came from; if I had to venture a guess I would suggest QQ candy, a gummy candy that first appeared in the late 90s which has the same kind of texture.

"Q" originated as a Taiwanese morpheme that has no agreed upon character.

This definition of "Q" is not to be confused with another definition, as a short-hand for "cute".