A bicycle operating device comprises a mounting clamp and an adapter member. The mounting clamp is configured to be mounted to a bicycle tube member and comprises a first radius portion, a second radius portion, and a clamp opening. The first radius portion defines a first inner radius. The second radius portion defines a second inner radius different from the first inner radius. The bicycle tube member is to extend through the clamp opening. The clamp opening is defined by the first radius portion and the second radius portion. The adapter member is configured to be provided between the second radius portion and the bicycle tube member in a state where the mounting clamp is mounted to the bicycle tube member.