I'm not sure that how Project-Based Learning can be used in Biology Olympiads. Any way this is enough potential to be used for assessing for understanding.
To examine Project-Based Learning in practice, we chose a lower secondary school situated in North East of Tehran during the school year 2001-2 More than 150 students involved in our work were grouped into 50 groups of 2-4 people: each group defined its favorite project, supervised by a mentor.

The groups started their activities on the selected project at the beginning of October, while the new school year starts in Iran and students are just come back to school. The duration of time for the project were defined around 4 months, i.e. till end of January.

The project underwent diversity in content and requirements. While some demanded collecting information, others required making one or more artifacts, and/or a combination of both.

Time dedicated to projects was totally chosen from student’s free time including holydays, when the students were just out of school.

Each group was to present its own results as attractive as possible, using different media they were able to apply.

Some successful projects were entitled as below. 

-         Escalator

-         Microwave oven

-         Dentistry row materials

-         Fridge

-         Rope way

-         Laser, production and application

Some project rose support from students’ family members, so they got favourable helps. This lead to a collaboration needed for science works, i.e. to collect information, visiting required places etc. As some projects involved the students in a real science project, they had a useful practice of science process skills e.g. designing experiments, collecting, presenting, and analysis and interpreting of data.

Because all students were involved in the activities enthusiastically mentors were satisfied observing their students in scientific research they were involved.

Assessing students project were consider upon assessing for understanding. That was not done by teacher or supervisor, but only considered by visitors.

The school continue to introduce projects as extracurricular activities for students after the first year of implementation.