You manage an App Engine Service that aggregates and visualizes data from BigQuery.

The resource that you need to get access is in the other project.

roles/bigquery.dataViewer BigQuery Data Viewer

When applied to a table or view, this role provides permissions to:

Read data and metadata from the table or view.

This role cannot be applied to individual models or routines.

When applied to a dataset, this role provides permissions to:

Read the dataset's metadata and list tables in the dataset.

Read data and metadata from the dataset's tables.

When applied at the project or organization level, this role can also enumerate all datasets in the project. Additional roles, however, are necessary to allow the running of jobs.