A vehicle having an adjustable seating assembly and related method. One member of the seating assembly may be adjusted to provide a backrest to a straddle type seat of the vehicle. As such, when a carrier bed having an accessory platform is located rearward of the straddle type seat, the one member may optionally be used to provide a wall portion of the carrier bed. The one member may also be adjusted to provide an extension to the straddle type seat. As such, when an accessory platform is located rearward of the straddle type seat, the one member may optionally be used to at least partially cover a segment of the accessory platform. When an accessory platform is located rearward of the straddle type seat, an additional member of the seating assembly may be adjusted to provide a backrest to one or more of the straddle type seat or an extended straddle type seat. The additional member may also be adjusted to form a segment of the accessory platform.