The Oak Ridge Boys will be in the nation's Capitol again today where they will perform at another major event. Last night, they performed at the Third Annual Congressional Awards Gala at the newly completed Ronald Reagan International Trade Center. The awards honor young Americans between ages 14 and 23 for their volunteer public service and personal achievement. Grant Hill, star of the Detroit Pistons, received the Horizon Award in recognition of his lifetime accomplishments and dedication to youth. Today, the Oaks will join Garth Brooks as performers at the American Red Cross 50th Anniversary of Blood Services. Throughout the day, the group will be singing, speaking and participating in a Red Cross exhibit tour. President Clinton is expected to attend today's daytime event.