The GitHub web UI for adding access to repos for organization teams is pretty terrible. Luckily the API is pretty robust.

grant.py

import re
import sys
from pygithub3 import Github
# Notice: there is a requirements.txt file to help you get pygithub3 via...
# pip install -r requirements.txt

if __name__ == '__main__':
    larg = len(sys.argv)
    if larg < 5 or larg == 6 or (larg > 7 and sys.argv[5] != '--include'):
        print "    {command} username password oranization team [--include 'RegularExpression']". format(command=sys.argv[0])
        sys.exit()
    regex = re.compile('.')
    if larg == 7:
        if sys.argv[5] == '--include':
            regex = re.compile(sys.argv[6])

    login = sys.argv[1]
    password = sys.argv[2]
    org = sys.argv[3]
    team = sys.argv[4]
    gh = Github(login=login, password=password)
    teams = gh.orgs.teams.list(org).all()
    team_id = [t.id for t in teams if t.name == team][0]
    all_repos = gh.repos.list_by_org(org).all()
    repo_names = filter(regex.search, [r.name for r in all_repos])

    print "login: {login}".format(login=login)
    print "org: {org}".format(org=org)
    print "team: {team}".format(team=team)
    print "team_id: {team_id}".format(team_id=team_id)
    print "repos: {repos}".format(repos=', '.join(repo_names))

    response = raw_input('proceed with these values? [Ny] ').lower()
    if response != 'y':
        sys.exit()

    for repo in repo_names:
        gh.orgs.teams.add_repo(id=team_id, user=org, repo=repo)

require.txt

pygithub3>=0.5