The University of Maryland's women's gymnastics team will replace the M.G.'s of Silver Spring today in the first Nation's Capital Cup gymastics meet, featuring several of the country's top teams in competition at Cole Field House.

The M.G.'s were ousted from the tournament when promoters discovered that Stephanie Willim, the M.G.'s top performer and a strong drawing card, would not be participating. The 13-year-old Willim is at a training camp in California.

Maryland's Bob Wall,who is coordinating the tournament, said the promoters felt they had been deceived by her coach. Greg Weiss, whom they said led them to believe Willim would be taking part.

"Even if he walked in here right now with Stephanie, we wouldn't let them (the M.G.'s and Willim) compete," Wall said yesterday. "He knew (she wouldn't participate) and he could have let us know."

Wall said no one knew she would not be appearing until Monday when The Post ran a story saying so.

Weiss said that Ruth Ann McBride of MarVa Teens, who was helping Wall with the meet, knew of the California training camp and had tried to arrange for Willim and others to be excused early.

Weiss added that Willim could not get back here before 4 a.m. today and he didn't want to "pull her off a plane at that hour" and have her performing at 1:30 p.m. when the team competition begins. The individual competition is at 7:30 p.m. and separate admissions will be charged.

Regardless, the meet will feature eight outstanding teams competing in four Olympic events: balance beam, uneven bars, vault and floor exercise. Besides awards in these categories, there is also an "overall" best award.

Heading the list of teams is the 1977 national club champions, the National Academy of Artistic Gymnasts of Oregon, which has produced more Olympians than any other club in the country.

One of California's best teams, the KIPS, are entered, with Donna Turnbow, the 1977 all-around club champions in the senior elite division. Turnbow is recovering from a broken ankle and will not vault or do floor exercises.

Pennsylvania's four-time state champion. Joanne Beltz, who is also the 1977 senior advanced champion (one step below elite), will compete along with her Parkette teammates from Allentown.

Other top entries include the Gym-Dandies from Washington Pa., with junior elite gymnast Linda Kardos and the Connecticut Gymnastics Club with 11-year-old Jackie Cassello.

The Palestrum All-Stars, another group of outstanding gymnasts, will also be on hand.

The MarVa Teens of Rockville, featuring Jenny Huff, round out the meet, which is one of the few annually to bring such top competition together.

After having Soviet gymnast Olga Korbut at Cole twice and Romanian Nadia Comaneci once. Wall said he began to think "an awful lot of money (two-thirds of the gate) is going out of the country. So I asked Ruth Ann McBride one day, can't (Americans) do something like this?

"When you watch the Olympics, you wonder, 'Where are the Americans? Why are just the Eastern bloc nations the only ones to make the finals?' One of the reasons is that the Americans don't have many opportunities to get together at meets like this where the competition is strong."

For the 1:30 p.m. team competition, all tickets are $2. For the 7:30 p.m. individual competition, the price is $3 for general admission and $5 reserved.