volunteer as

volunteer as (something)

1. To choose or offer to assume or fulfill some role or position without being asked, directed, or required to do so. I don't know why everyone thinks I volunteered as class secretary, because I definitely didn't! She volunteered as the spokesperson of the group.
2. To perform some role or duty without pay, as for charity. I volunteer as a firefighter on the weekends. Why don't you volunteer as a reader down at the retirement home? They would really appreciate your help.
See also: volunteer

volunteer for (something)

To choose or offer to assume or undertake some position, role, or duty without being asked, directed, or required to do so. I know you didn't volunteer for this responsibility, but you've done an admirable job filling in after Jack left the company. She volunteered for the role, not realizing how much additional work it entailed.
See also: volunteer
Farlex Dictionary of Idioms.

volunteer as something

to submit oneself as a person ready or willing to do something. Would you be willing to volunteer as a marcher? I will volunteer as a helper in the hospital.
See also: volunteer
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.
See also:
  • volunteer as (something)
  • assume the position
  • strike a pose
  • strike a pose/an attitude
  • strike an attitude
  • play a part in
  • play a part in (something)
  • bring (someone or something) under (one's) control
  • bring under control
  • bring/get/keep something under control
References in periodicals archive
Webster's Dictionary simply defines a volunteer as "one who enters into or offers oneself for a service of his/her free will." (1) A volunteer is not coerced to perform services, but donates time, skills and knowledge willingly to help without normally expecting compensation.
"We notify members of activities in their area, and they can choose to volunteer as time permits," says Tracie Jones, program coordinator for CAN.