Certain aspects of the present disclosure provide methods and apparatus for multiuser transmission during a grant to utilize unused portion of a transmit opportunity (TXOP) that is assigned to an initiator device. A responder device may receive, from an initiator device, at least one grant to utilize unused portion of the TXOP. In response to the grant and during the unused portion of the TXOP, The responder device may transmit a first message intended for the to the initiator device, and one or more messages intended for one or more other stations using multi-user transmission schemes. The messages transmitted to stations other than the initiator device may include an indication that the station does not need to respond (e.g., with an acknowledgment) upon receipt of the message.