The avalanche hit at about noon as a group of eight was skiing in the remote and mountainous area near Cornucopia, Baker County Sheriff Mitch Southwick said in a written statement.
Most of the skiers are from the Seattle area. Officials weren't releasing their names or ages until family members could be notified.
Officials said a LifeFlight helicopter was dispatched to rescue the survivors but could not get closer than 1.5 miles from the skiers.
Two medics were with the injured skiers Tuesday night as rescue efforts continued, Undersheriff Warren Thompson said. A woman suffered two broken legs and a shoulder injury while a man had a broken thigh bone, Thompson said.
The unhurt skiers were at a nearby cabin, the undersheriff said.
Low cloud cover and the 7,000-foot elevation made the rescue more difficult.
In addition to ground crews, both an Oregon National Guard helicopter and an Idaho National Guard helicopter were part of the rescue effort, Thompson said.
Connelly Brown, the owner of Wallowa Alpine Huts, said the skiers were part of a backcountry skiing group organized by his Joseph-based company. The group included two guides and six skiers.
Brown said a guide contacted him by cellphone after the avalanche hit, reporting two possible fatalities and two skiers with broken legs. The skiers were on a guided five-day, four-night trip, he said.
The avalanche came down on the third day of the trip, Brown said. Later that night, as on previous nights, the group planned to sleep at the Schneider Cabin, a historic miners' log cabin on the south side of Cornucopia Peak.
Brown said the clients and the guides are all "fit, proficient downhill skiers." The guides were certified by the American Institute for Avalanche Research and Education and trained by the American Mountain Guide Association, he said.
"From the description, it sounded like they were traveling and the avalanche came from above and caught them by surprise," Brown said.
The avalanche occurred in the southern part of the Wallowa Mountains, near the Idaho border. The Wallowas are known as the "Alps of Oregon." With their rocky peaks and deep ravines, the mountains are popular with backcountry skiers, hikers and horseback riders.
A bulletin from the Wallowa Avalanche Center on Thursday warned that "new snow is not bonding well to the old surface." The bulletin mentioned a recent report from the southern Wallowas of a skier triggering a small avalanche in which no one was caught.
The deaths mean at least 12 people have died in avalanches nationally this season, including six since Sunday. Kevin Kuybus, 46, of Highlands Ranch, Colo., was found dead Tuesday after an avalanche outside a Colorado ski area. Another avalanche near Kebler Pass, Colo., killed a snowmobiler Monday, and two people died in slides in Utah over the weekend.