Eaton, the Olympic and World decathlon champion, captured the non-decathlon event of 400m hurdles in 49.16 seconds.
It was .09 of a second slower than his personal best from Sunday, but Eaton beat an Oslo field that included 2011 World bronze medalist LJ Van Zyl.
Eaton is focusing on the 400m hurdles this season since there are no Olympics or World Championships to defend his decathlon titles.
He is the 10th fastest 400m hurdles man this year and said he would like to break 49 seconds in his next meet, Tuesday in the Czech Republic.
Felix took the 200m in 22.73, continuing her comeback from a torn hamstring at the 2013 World Championships.
The six-time Olympic medalist actually ran .29 faster in Eugene, Ore., two weeks ago, when she finished third against a stronger field.
The Diamond League moves to New York for the Adidas Grand Prix on Saturday.
In other Oslo events, Galen Rupp followed up his 10,000m American record from Eugene with a third-place finish in the 5000m. Rupp clocked 13:03.35, 10 seconds slower than Bernard Lagat‘s American record. Ethiopian Yenew Alamirew won in 13:01.57.
Trinidad and Tobago’s Richard Thompson won the 100m in 10.02, .02 faster than France’s Jimmy Vicaut. The event was missing stars Usain Bolt, Yohan Blake, Justin Gatlin and Tyson Gay.
Djibouti’s Ayanleh Souleiman edged New Zealand’s Nick Willis in the Dream Mile, 3:49.49 to 3:49.83. American Matthew Centrowitz was eighth in 3:52.23.
Olympic champion and world record holder Renaud Lavillenie stayed perfect on the Diamond League season with a 5.77m pole-vault clearance.
Olympic silver medalist Will Claye won his third straight triple jump competition (17.41m), topping Olympic champion Christian Taylor (17.15m). Brit Phillips Idowu, on the comeback trail after winning medals at every global championship from 2008 through 2011, was eighth and last at 16.30m.
American Joe Kovacs upset Olympic and World shot put medalists David Storl, Reese Hoffa, Tomasz Majewski and Christian Cantwell with a 21.14m throw.
Olympic and World high jump champions Anna Chicherova and Blanka Vlasic were beaten by Russian World Indoor champion Mariya Kuchina, who leaped 1.98m.
Jamaican Novlene Williams-Mills, a breast cancer survivor, won the women’s 400m in 50.06, ahead of American Natasha Hastings (50.6) and 2011 World champion Amantle Montsho of Botswana (51.05).
Kenyan Eunice Sum took the 800m in 1:59.02, ahead of American World bronze medalist Brenda Martinez (1:59.68). South African Caster Semenya was 12th out of 12 finishers in 2:03.68.
France’s Pascal Martinot-Lagarde took the 110m hurdles in 13.12, the fastest time in the world this year. He smashed a field that included the four reigning Olympic and World silver and bronze medalists by .24.