Once the (first version of the) Outcome Challenge is formulated for each of the boundary partners, participants of an Intentional Design workshop will develop a set of progress markers for each Outcome Challenge statement. Here are three approaches that I have come across and used to facilitate this step. 

1/ Participants are asked to look at the Outcome Challenge as a whole, to read it a few times and to reflect individually or in pairs on the question ‘Which intermediate outcomes/milestones (still written as a behavioral change) are expected (and can be observed) that would show that we are moving towards the achievement of the outcome challenge?’.

After this reflection, the facilitator collects all the ideas together in the plenary (or in a smaller sub-group looking at a particular boundary partner) and guides a process of further discussion, prioritisation to finally come to a set of progress markers that are clustered with the participants into ‘expect to see', 'like to see' and 'love to see'. 

2/ Participants are asked to look at the Outcome Challenge and reflect on each major behavioural change decribed in the OC separately, i.e. people discuss (in pairs or in group) on possible intermediate outcomes/milestones for that specific ideal change. After every elements of the OC has been looked at, the facilitator brings everything together and facilitates a process of deleting similar ideas, fine-tuning and re-phrasing the PMs,  combining ideas leading to a prioritisation and clustering of the PMs into ‘expect to see', 'like to see' and 'love to see'.

3/ A third alternative approach starts the same as the second approach, except that participants are asked to formulate 3 observable intermediate outcomes/milestones for each single element of the OC statement, i.e. one expect to see miliestone,  one like to see milestone, one love to see milestone. This is a more systematic - some might  say a more artificial approach - but the advantage is that it generate lots of possible progress markers. After this process, the facilitators brings all the possible progress markers together (most likely you’ll end up with too many) and again a process of discussion, deleting overlaps, combining  similar ideas and prioritisation of the most relevant progress markers is necessary.

Some things to consider

• After this process, the facilitator could ask participants to critically look at the progress markers and cross-check whether they have formulated PMs as behavioral changes and whether those changes are observable. 
• It is important that the full set of PMs makes sense as a whole makes for the participants that developed them. People should afterwards have the feeling that the set of PMs is something that is achievable, realistic and that motivates them – something they want go for.
• During the process of developing relevant progress markers, it might happen (and sometimes it good to cross-check it during the process) that elements of the original Outcome Challenge are moved as a progress marker because the level of change was too low and vice versa that some PMs are actually better places as an elements of an OC because they describe a more ideal change.
• From a monitoring/learning perspective it is important that people have the feeling that the PMs are rightly chosen and will potentially generate interesting insights (and trigger learning) about the progress of the programmes and future actions.